Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, net	$ (30,949)		$ (30,949)		$ (36,050)	$ (61,511)
Accrued expenses and other current liabilities	(43,138)		(43,138)		(8,271)	(10,908)
Lease financing obligations, net of current portion	0		0		0	$ (22,987)
Total operating lease costs	2,134		6,421
Cash payments for operating leases	$ 2,400	$ 2,500	$ 7,000	$ 7,300
Weighted average remaining lease term	7 years 1 month 6 days		7 years 1 month 6 days
Weighted average discount rate	5.70%		5.70%
Sublease income	$ 500	$ 600	$ 1,500	$ 1,600
Adjustments Due to Adoption of New Leasing Standard
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, net					25,461
Accrued expenses and other current liabilities					2,637
Lease financing obligations, net of current portion					22,987
Adjustments Due to Adoption of New Leasing Standard | Capitalized facility leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, net					28,300
Accrued expenses and other current liabilities					1,800
Lease financing obligations, net of current portion					$ 23,000
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining lease terms			1 year
Lease renewal term	3 years		3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining lease terms			11 years
Lease renewal term	5 years		5 years