Right-of-Use ("ROU") Assets and Lease Liabilities - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Operating leases:
Lease cost	$ 9,700	$ 8,335	$ 26,615	$ 24,469
Variable lease cost	283	527	3,128	2,852
Operating lease cost	9,983	8,862	29,743	27,321
Finance leases:
Amortization of ROU assets	734	615	2,136	2,044
Interest on lease liabilities	73	106	246	347
Finance lease cost	807	721	2,382	2,391
Total lease cost	$ 10,790	$ 9,583	32,125	29,712
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases			22,336	20,035
Financing cash flows from finance leases			2,066	2,002
ROU assets obtained in exchange for lease obligations:
Finance leases			205	203
Operating leases			$ 29,513	$ 136,204
Operating Leases
Weighted average remaining lease term (years)	5 years 2 months 4 days		5 years 2 months 4 days		5 years 3 months 25 days
Weighted average discount rate	4.00%		4.00%		4.40%
Finance Leases
Weighted average remaining lease term (years)	2 years 5 months 26 days		2 years 5 months 26 days		3 years 3 months 3 days
Weighted average discount rate	5.20%		5.20%		5.20%