Derivative Instruments (Derivative Call Options and Interest Rate Swaps by Counterparty) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative instruments	$ 684,033	$ 431,727	[1]
Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	39,414,367	39,335,903
Derivative instruments	684,033	430,558
Bank of America | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	3,913,403	3,574,125
Derivative instruments	45,365	26,080
Barclays | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,910,246	3,686,896
Derivative instruments	60,478	39,657
Canadian Imperial Bank of Commerce | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,442,141	2,707,734
Derivative instruments	54,020	34,218
Citibank, N.A. | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	4,132,309	3,748,162
Derivative instruments	49,853	29,873
Credit Suisse | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,074,458	2,086,470
Derivative instruments	36,903	20,691
J.P. Morgan | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	6,153,747	6,501,103
Derivative instruments	78,007	69,006
Mizuho | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	691,141	0
Derivative instruments	19,273	0
Morgan Stanley | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,569,596	2,957,389
Derivative instruments	36,543	38,470
Royal Bank of Canada | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	4,595,241	4,378,132
Derivative instruments	102,189	58,026
Societe Generale | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,460,528	2,099,081
Derivative instruments	36,410	17,157
Truist | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	2,142,918	1,960,787
Derivative instruments	49,287	32,885
Wells Fargo | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	5,200,545	5,436,824
Derivative instruments	113,323	61,840
Exchange traded | Call Options and Interest Rate Swaps
Derivative [Line Items]
Notional amount	128,094	199,200
Derivative instruments	$ 2,382	$ 2,655

[1] Certain prior period amounts have been recast. See Note 1 - Significant Accounting Policies for more information.