Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 15,425,954,000	$ 14,419,133,000
Gross Unrealized Gains	44,591,000	163,823,000
Gross Unrealized Losses	(690,051,000)	(132,929,000)
Allowance for Credit Losses	0	0
Fair Value	14,780,494,000	14,450,027,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,115,041,000	1,035,477,000
Gross Unrealized Gains	28,002,000	47,484,000
Gross Unrealized Losses	(13,082,000)	(2,241,000)
Allowance for Credit Losses	0	0
Fair Value	1,129,961,000	1,080,720,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,765,000	50,773,000
Gross Unrealized Gains	0	1,901,000
Gross Unrealized Losses	(4,375,000)	(919,000)
Allowance for Credit Losses	0	0
Fair Value	51,390,000	51,755,000
State and Municipal Obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,161,006,000	2,072,210,000
Gross Unrealized Gains	7,073,000	41,540,000
Gross Unrealized Losses	(95,814,000)	(16,923,000)
Allowance for Credit Losses	0	0
Fair Value	2,072,265,000	2,096,827,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,774,953,000	5,698,088,000
Gross Unrealized Gains	5,662,000	52,676,000
Gross Unrealized Losses	(339,241,000)	(67,764,000)
Allowance for Credit Losses	0	0
Fair Value	5,441,374,000	5,683,000,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,525,223,000	1,383,037,000
Gross Unrealized Gains	250,000	681,000
Gross Unrealized Losses	(90,110,000)	(17,241,000)
Allowance for Credit Losses	0	0
Fair Value	1,435,363,000	1,366,477,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,121,388,000	3,546,024,000
Gross Unrealized Gains	3,097,000	12,921,000
Gross Unrealized Losses	(113,124,000)	(19,726,000)
Allowance for Credit Losses	0	0
Fair Value	4,011,361,000	3,539,219,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,421,564,000	10,627,149,000
Gross Unrealized Gains	9,009,000	66,278,000
Gross Unrealized Losses	(542,475,000)	(104,731,000)
Allowance for Credit Losses	0	0
Fair Value	10,888,098,000	10,588,696,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	672,578,000	633,524,000
Gross Unrealized Gains	507,000	6,620,000
Gross Unrealized Losses	(34,305,000)	(8,115,000)
Allowance for Credit Losses	0	0
Fair Value	$ 638,780,000	$ 632,029,000