Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Derivative [Line Items]
Net unrealized gains (losses) arising during the period	$ (111,549,000)	$ (8,081,000)	$ (284,216,000)	$ (39,061,000)
Unrealized gain, after tax	(84,967,000)	(6,037,000)	(216,531,000)	(28,657,000)
Income recognized	690,000	4,000,000	3,900,000	9,300,000
Cash flow hedge gain (loss) to be reclassified			(138,000,000)
Cash flow hedge termination gain			1,000,000
Collateral requirements	58,600,000		58,600,000		$ 64,500,000
Cash Flow Hedges
Derivative [Line Items]
Net unrealized gains (losses) arising during the period	0	488,000	0	1,200,000
Unrealized gain, after tax		$ 364,000		$ 930,000
Cash Flow Hedges | Forward-Starting Cash Flow Hedges Added In Q3 QTD 2022
Derivative [Line Items]
Increase in derivative, notional amount	0
Cash Flow Hedges | Forward-Starting Cash Flow Hedges Added In Q3 YTD 2022
Derivative [Line Items]
Increase in derivative, notional amount			1,650,000,000
Fair Value Hedges | Interest rate contracts
Derivative [Line Items]
Increase in derivative, notional amount	$ 947,100,000		$ 1,770,000,000