Investment Securities (Narrative) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Percentage decrease requiring a review for impairment	20.00%
Fair value of securities on impairment watch list	$ 106,400		$ 13,400
Debt Securities, Available-for-sale, Unrealized Loss Position	12,441,342		9,047,662
Unrealized Loss on AFS Debt Securities	1,092,122		132,929
AFS securities in loss position at period-end, change in unrealized loss	959,200
Securities pledged as collateral	5,300,000		6,400,000
Securities pledged as collateral and may be sold or re-pledged	$ 209,900
Number of investments in a single issuer that exceed 10% of stockholder's equity	0
No investment in a single issuer exceeds this percentage of stockholder's equity	10.00%
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
U.S. Treasury inflation-protected securities held, at fair value	$ 383,700
Debt Securities, Available-for-sale, Unrealized Loss Position	609,636		296,492
Unrealized Loss on AFS Debt Securities	20,883		$ 2,241
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Losses realized on sales	(9,582)	$ 0
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Equity Securities, FV-NI, Unrealized Gain (Loss)	(1,023)	15
Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Other Securities, Loss realized on sales	(4,313)	0
Fair value other securities adjustments, net	$ 23,083	$ 25,031