Summary of Significant Accounting Policies - Leases (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) Option	Mar. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Variable lease expense and short-term lease expenses	$ 1,900
Weighted average discount rate	4.10%
Lease expense	$ 5,600	$ 5,200
Weighted average remaining lease term	8 years 7 months 6 days
Rent paid to related parties	$ 1,200	$ 1,100
Existence of option to extend	true
Summary of lease asset and liabilities
Lease right-of-use assets	$ 70,316
Lease Liabilities
Other current liabilities	$ 11,066
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current
Lease liabilities	$ 62,028
Present Value of Lease Liabilities	73,094
Maturities of lease liabilities:
2019 (excluding the three months ended March 31, 2019)	10,687
2020	12,508
2021	11,341
2022	9,410
2023	7,821
Thereafter	35,541
Total Lease Payments	87,308
Less-Interest	(14,214)
Present Value of Lease Liabilities	73,094
Supplemental information related to leases:
Cash paid for amounts included in the measurement of lease liabilities	5,904
Lease right-of-use assets obtained in exchange for lease liabilities	$ 174
Minimum
Lessee, Lease, Description [Line Items]
Lease term	3 years
Number of options to renew | Option	1
Maximum
Lessee, Lease, Description [Line Items]
Lease term	10 years