Leases (Details) £ in Thousands, ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2021 USD ($) ft²	Dec. 31, 2021 GBP (£)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 49,580		$ 48,561	$ 41,257
Variable Lease, Cost		6,062		7,490	8,474
Operating Lease, Payments		45,886		30,709	20,175
Operating Lease, Incentive Payments Received		9,216		14,732	18,771
Lessee, Additional Payments for Operating Leases Not Yet Commenced		$ 232,267
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract		13 years
Letter of Credit [Member]
Lessee, Lease, Description [Line Items]
Other Assets		$ 5,616		5,550
Office Equipment [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost		$ 5,193		$ 4,709	$ 4,107
Building [Member] | UNITED KINGDOM
Lessee, Lease, Description [Line Items]
Net Rentable Area | ft²		14
Building [Member] | United States [Member]
Lessee, Lease, Description [Line Items]
Net Rentable Area | ft²		30
Building [Member] | Annual Expense | UNITED KINGDOM
Lessee, Lease, Description [Line Items]
Operating Lease, Cost | £			£ 1,081
Building [Member] | Annual Expense | United States [Member] | Subsequent Event [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	$ 2,200