Derivative Financial Instruments - Notional Values (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	$ 8,600,000
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	8,557,883	$ 9,926,864
Interest Rate Swaps | Trading
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	2,693,364	3,744,917
Interest Rate Swaps | Cash Flow | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	1,018,976	1,150,518
Interest Rate Swaps | Fair Value | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	$ 4,845,543	$ 5,031,429