Derivative Instruments Derivative Instruments - Notional and Fair Value Amounts of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative assets, weighted average pay rate	1.21%
Derivative assets, notional amount	$ 1,001,715	$ 0
Derivative assets, fair value	13,948	0
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative assets, notional amount	316,357	408,881
Derivative assets, fair value	17,661	35,846
Derivative liability, notional amount	320,001	417,941
Derivative liabilities, fair value	$ 17,825	$ 36,141