Leases (Details) $ in Thousands		12 Months Ended
	Jul. 01, 2018 Floor	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 48,561	$ 41,257
Variable Lease, Cost		7,490	8,474
Operating Lease Additional Floors | Floor	7
Operating Lease Additional Floors Commencing on Lease Effective Date | Floor	3
Operating Lease, Payments		30,709	20,175
Operating Lease, Incentive Payments Received		14,732	18,771
Operating Lease Right-of-Use Assets		270,498	199,988
Lessee, Additional Payments for Operating Leases Not Yet Commenced		$ 195,651
Operating Lease, Term To Take Remaining Floors		3 years
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		13 years
Accounting Standards Update 2016-02 [Member]
Lessee, Lease, Description [Line Items]
Operating Lease Right-of-Use Assets				$ 180,935
Office Equipment [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 4,709	4,107
Letter of Credit [Member]
Lessee, Lease, Description [Line Items]
Other Assets		$ 5,550	$ 5,536