Right-of-Use ("ROU") Assets and Lease Liabilities - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Operating leases:
Lease cost	$ 8,125	$ 8,082	$ 16,915	$ 16,134
Variable lease cost	1,585	1,272	2,845	2,325
Operating lease cost	9,710	9,354	19,760	18,459
Finance leases:
Amortization of ROU assets	801	761	1,402	1,429
Interest on lease liabilities	82	117	173	241
Finance lease cost	883	878	1,575	1,670
Total lease cost	$ 10,593	$ 10,232	21,335	20,129
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases			14,752	13,345
Financing cash flows from finance leases			1,355	1,319
Right-of-use-assets obtained in exchange for lease obligations:
Finance leases			169	203
Operating leases			$ 22,022	$ 126,565
Operating Leases
Weighted average remaining lease term (years)	5 years 3 months 21 days		5 years 3 months 21 days		5 years 3 months 25 days
Weighted average discount rate	4.10%		4.10%		4.40%
Finance Leases
Weighted average remaining lease term (years)	2 years 8 months 19 days		2 years 8 months 19 days		3 years 3 months 3 days
Weighted average discount rate	5.20%		5.20%		5.20%