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Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Derivative [Line Items]
Net unrealized gains (losses) arising during the period	$ (135,978,000)	$ (29,057,000)
Unrealized gain, after tax	(103,617,000)	(21,183,000)
Income recognized	2,200,000	1,600,000
Cash flow hedge gain (loss) to be reclassified	26,000,000
Cash flow hedge termination gain	3,000,000
Collateral requirements	46,200,000		$ 64,500,000
Variation margin, amount reducing derivative asset	61,400,000		$ 94,600,000
Cash Flow Hedges
Derivative [Line Items]
Net unrealized gains (losses) arising during the period	0	757,000
Unrealized gain, after tax		$ 565,000
Cash Flow Hedges | Forward-Starting Cash Flow Hedges added in Q1 2022
Derivative [Line Items]
Notional amount	$ 1,400,000,000

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