Lease Agreements - Company as Lessee - Narrative and Components of Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Office lease, renewal term	5 years
Operating lease right-of-use assets	$ 72,143	$ 74,744
Total leased assets	72,143	74,744
Operating lease liabilities	74,037	76,740
Total lease liabilities	74,037	76,740
Lease, Cost [Abstract]
Operating lease cost	6,749	6,745
Variable lease cost	1,436	783
Short-term lease cost	432	610
Sublease income	(438)	(436)
Total lease cost	8,179	7,702
Operating lease right-of-use assets
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	72,143	74,744
Operating lease liabilities
Lessee, Lease, Description [Line Items]
Operating lease liabilities	$ 74,037	$ 76,740
Minimum
Lessee, Lease, Description [Line Items]
Office lease term of contract	5 years
Ground lease term	20 years
Ground lease, renewal term	10 years
Maximum
Lessee, Lease, Description [Line Items]
Office lease term of contract	10 years
Ground lease term	85 years
Ground lease, renewal term	39 years