Leases (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Jul. 01, 2018 Floor	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 12,248	$ 10,649	$ 36,272	$ 30,992
Variable Lease, Cost		1,841	1,754	4,696	6,572
Operating Lease Additional Floors | Floor	7
Operating Lease Additional Floors Commencing on Lease Effective Date | Floor	3
Operating Lease, Payments				22,469	15,778
Operating Lease, Incentive Payments Received				10,267	12,854
Lessee, Additional Payments for Operating Leases Not Yet Commenced		$ 197,835		$ 197,835
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		3 years		3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		13 years		13 years
Office Equipment [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 1,170	$ 1,132	$ 3,497	$ 3,059
Letter of Credit [Member]
Lessee, Lease, Description [Line Items]
Other Assets		$ 5,549		$ 5,549		$ 5,536