Update to Significant Accounting Policies - Impact of Corrections on Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Dec. 30, 2018	Apr. 01, 2018	Dec. 31, 2017
Percentage of domestic restaurants franchised	80.00%
Assets
Cash and cash equivalents	$ 29,273		$ 33,258
Accounts receivable, net	80,748		78,118
Income tax receivable	5,431		16,146
Prepaid expenses	22,488	$ 25,707	30,376
Other current assets	18,582		5,678
Total current assets	199,414		196,277
Deferred income taxes, net	1,244		1,137
Total assets	739,068		595,897
Current liabilities:
Accounts payable	35,214		27,106
Accrued expenses and other current liabilities	120,975		129,167
Deferred revenue current	2,516		2,598
Current portion of long-term debt	29,982		20,009
Total current liabilities	218,569		185,470
Deferred revenue	18,562		20,674
Total liabilities	795,677		894,446
Retained earnings	231,439		242,182
Total stockholders' equity (deficit)	(313,258)		(304,013)	$ (251,360)	$ (105,954)
Total liabilities, redeemable noncontrolling interests, Series B preferred stock and stockholders’ (deficit)	$ 739,068		595,897
As reported
Assets
Cash and cash equivalents			19,468
Accounts receivable, net			67,854
Income tax receivable			16,073
Prepaid expenses			29,935
Other current assets			5,677
Total current assets			171,708
Deferred income taxes, net			756
Total assets			570,947
Current liabilities:
Accounts payable			29,891
Accrued expenses and other current liabilities			105,712
Deferred revenue current			2,443
Current portion of long-term debt			20,000
Total current liabilities			164,636
Deferred revenue			14,679
Total liabilities			867,617
Retained earnings			244,061
Total stockholders' equity (deficit)			(302,134)
Total liabilities, redeemable noncontrolling interests, Series B preferred stock and stockholders’ (deficit)			570,947
Total Adjustments
Assets
Cash and cash equivalents			13,790
Accounts receivable, net			10,264
Income tax receivable			73
Prepaid expenses			441
Other current assets			1
Total current assets			24,569
Deferred income taxes, net			381
Total assets			24,950
Current liabilities:
Accounts payable			(2,785)
Accrued expenses and other current liabilities			23,455
Deferred revenue current			155
Current portion of long-term debt			9
Total current liabilities			20,834
Deferred revenue			5,995
Total liabilities			26,829
Retained earnings			(1,879)
Total stockholders' equity (deficit)			(1,879)
Total liabilities, redeemable noncontrolling interests, Series B preferred stock and stockholders’ (deficit)			$ 24,950