Investment Securities (Summary of Held-to-Maturity Debt Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Amortized Cost	$ 7,680,075	$ 7,074,797
Unrealized Gains	13,692	22,167
Unrealized Losses	(910,900)	(832,341)
Fair Value	6,782,867	6,264,623
Allowance	184	209	$ 282	$ 182
Net Carrying Value	7,679,891	7,074,588
Interest receivable	22,600	24,900
Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	432,551	433,554
Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	6,832,510	6,221,233
Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	252,852	253,671
Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	111,277	115,404
Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	32,690	32,732
Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	14,030	14,038
Agency CMO
Schedule of Investments [Line Items]
Amortized Cost	22,489	23,470
Unrealized Gains	0	0
Unrealized Losses	(1,938)	(1,728)
Fair Value	20,551	21,742
Allowance	0	0
Net Carrying Value	22,489	23,470
Agency CMO | Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMO | Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	22,489	23,470
Agency CMO | Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMO | Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMO | Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMO | Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency MBS
Schedule of Investments [Line Items]
Amortized Cost	2,618,783	2,409,521
Unrealized Gains	1,429	1,141
Unrealized Losses	(327,351)	(284,776)
Fair Value	2,292,861	2,125,886
Allowance	0	0
Net Carrying Value	2,618,783	2,409,521
Agency MBS | Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency MBS | Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	2,618,783	2,409,521
Agency MBS | Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency MBS | Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency MBS | Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency MBS | Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMBS
Schedule of Investments [Line Items]
Amortized Cost	4,028,799	3,625,627
Unrealized Gains	11,580	18,586
Unrealized Losses	(540,641)	(514,534)
Fair Value	3,499,738	3,129,679
Allowance	0	0
Net Carrying Value	4,028,799	3,625,627
Agency CMBS | Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMBS | Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	4,028,799	3,625,627
Agency CMBS | Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMBS | Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMBS | Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
Agency CMBS | Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	0	0
Municipal bonds and notes
Schedule of Investments [Line Items]
Amortized Cost	910,422	916,104
Unrealized Gains	683	2,440
Unrealized Losses	(34,953)	(24,877)
Fair Value	876,152	893,667
Allowance	184	209
Net Carrying Value	910,238	915,895
Municipal bonds and notes | Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	332,969	333,479
Municipal bonds and notes | Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	162,439	162,615
Municipal bonds and notes | Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	252,852	253,671
Municipal bonds and notes | Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	111,277	115,404
Municipal bonds and notes | Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	32,690	32,732
Municipal bonds and notes | Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	14,030	14,038
CMBS
Schedule of Investments [Line Items]
Amortized Cost	99,582	100,075
Unrealized Gains	0	0
Unrealized Losses	(6,017)	(6,426)
Fair Value	93,565	93,649
Allowance	0	0
Net Carrying Value	99,582	100,075
CMBS | Moody's, Aaa Rating
Schedule of Investments [Line Items]
Amortized Cost	99,582	100,075
CMBS | Moody's, Aa1 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
CMBS | Moody's, Aa2 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
CMBS | Moody's, Aa3 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
CMBS | Moody's, A1 Rating
Schedule of Investments [Line Items]
Amortized Cost	0	0
CMBS | Moody's, Not Rated
Schedule of Investments [Line Items]
Amortized Cost	$ 0	$ 0