Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Termination of office leases	$ 9,600	$ 66,500
Impairments of ROU assets	6,003	27,104
Write off of leasehold and fixed assets	3,000	37,900
Dilapidation charges	$ 600	$ 1,400
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract	1 year
Sublease, term of contract	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract	15 years
Sublease, term of contract	11 years