Leases - Net Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 140,829	$ 144,727
Variable lease cost	17,463	16,404
Sublease income	(38,925)	(38,901)
Total lease cost, net	119,367	122,230
Cash paid for amounts included in the measurement of operating lease liabilities	137,790	135,799
Cash receipts from sublease arrangements	38,565	34,441
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 27,258	$ 136,997
Weighted average remaining lease term for operating leases (in years)	9 years 7 months 6 days	10 years 2 months 12 days
Weighted average discount rate for operating leases	6.60%	6.70%
Cost of subleasing activities	$ 42,200	$ 43,200