Summary of Significant Accounting Policies - Summary of Impact of Adoption of Accounting Standards (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Prepaid expenses and other current assets	$ 22,624		$ 21,383
Total current assets	182,375		178,114
Property and equipment, net	37,639		52,255
Operating lease right-of-use assets	53,627		0
Total assets	1,006,517		967,933
Current liabilities:
Other current liabilities	18,425		4,861
Total current liabilities	264,541		257,026
Operating lease liabilities	46,238		0
Deemed landlord liability, less current portion	0		24,484
Deferred income tax liability	3,435		439
Other long-term liabilities	14,625		16,560
Total liabilities	384,620		378,230
Shareholders’ equity:
Accumulated deficit	(13,136)		(41,487)
Total shareholders’ equity	621,897		589,703	$ 526,473	$ 503,530
Total liabilities and shareholders’ equity	$ 1,006,517		$ 967,933
ASU 2016-02
Current assets:
Prepaid expenses and other current assets		$ 21,013
Total current assets		177,744
Property and equipment, net		37,613
Operating lease right-of-use assets		51,854
Total assets		1,004,775
Current liabilities:
Other current liabilities		10,951
Total current liabilities		263,116
Operating lease liabilities		45,294
Deemed landlord liability, less current portion		0
Deferred income tax liability		3,158
Other long-term liabilities		14,630
Total liabilities		405,919
Shareholders’ equity:
Accumulated deficit		(32,334)
Total shareholders’ equity		598,856
Total liabilities and shareholders’ equity		1,004,775
ASU 2016-02 | Adjustments
Current assets:
Prepaid expenses and other current assets		(370)
Total current assets		(370)
Property and equipment, net		(14,642)
Operating lease right-of-use assets		51,854
Total assets		36,842
Current liabilities:
Other current liabilities		6,090
Total current liabilities		6,090
Operating lease liabilities		45,294
Deemed landlord liability, less current portion		(24,484)
Deferred income tax liability		2,719
Other long-term liabilities		(1,930)
Total liabilities		27,689
Shareholders’ equity:
Accumulated deficit		9,153
Total shareholders’ equity		9,153
Total liabilities and shareholders’ equity		$ 36,842