Summary of Significant Accounting Policies - Leases (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Option	Jun. 30, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Variable lease expense and short-term lease expenses			$ 4,200
Weighted average discount rate	4.00%		4.00%
Lease expense	$ 6,200	$ 5,800	$ 11,800	$ 11,100
Weighted average remaining lease term	8 years 2 months 12 days		8 years 2 months 12 days
Rent paid to related parties	$ 700	$ 1,100	$ 2,000	$ 2,200
Existence of option to extend			true
Summary of lease asset and liabilities
Lease right-of-use assets	80,633		$ 80,633
Lease Liabilities
Other current liabilities	$ 13,185		$ 13,185
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current		Other Liabilities, Current
Long-term lease liabilities	$ 70,095		$ 70,095
Present Value of Lease Liabilities	$ 83,280		$ 83,280
Minimum
Lessee, Lease, Description [Line Items]
Lease term	3 years		3 years
Number of options to renew | Option			1
Maximum
Lessee, Lease, Description [Line Items]
Lease term	10 years		10 years