| Income taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) | Dec. 31, 2015 | Dec. 31, 2014 | 
|---|---|---|
| Deferred tax assets: | ||
| Deferred rent liabilities | $ 4,027,504 | $ 2,441,728 | 
| Lease incentives | 508,351 | 350,817 | 
| Stock compensation | 563,582 | 249,690 | 
| FICA tip credit carryforward | 1,421,757 | 767,816 | 
| Net operating loss | 1,899,676 | 84,833 | 
| Goodwill | 3,258,403 | 3,349,761 | 
| Derivative expense | 42,899 | 2,622,848 | 
| Inventory | 9,789 | 4,904 | 
| Charitable contributions carryforward | 6,131 | 0 | 
| Foreign tax credit carryforward | 109,957 | 0 | 
| Deferred revenue | 471,710 | 0 | 
| State and local tax credit carryforward | 243,508 | 0 | 
| Total deferred tax assets | 12,563,267 | 9,872,397 | 
| Deferred tax liabilities: | ||
| Depreciation and amortization | (2,352,575) | (2,129,646) | 
| Basis in LLC interest | (117,020) | 0 | 
| Total deferred tax liabilities | (2,469,595) | (2,129,646) | 
| Valuation allowance | 0 | (7,707,333) | 
| Net deferred tax assets | $ 10,093,672 | $ 35,418 | 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences for lease incentives. No definition available. 
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- Definition Deferred Tax Assets, Tax Credit Carryforwards, State and Local No definition available. 
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- Definition Amount of deferred tax liability attributable to taxable temporary differences. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible charitable contribution carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from derivative instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill. No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, before jurisdictional netting. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- References No definition available. 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign tax credit carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to other deductible tax credit carryforwards not separately disclosed. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred rent. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- References No definition available. 
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from investments (excludes investments in subsidiaries and equity method investments). No definition available. 
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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