Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 10,761,570	$ 8,581,829
Unrealized Loss, Less than 12 months	549,710	118,680
Fair Value, Greater than 12 months	1,467,196	465,833
Unrealized Loss, Greater than 12 months	140,341	14,249
Debt Securities, Available-for-sale, Unrealized Loss Position	12,228,766	9,047,662
Unrealized Loss on AFS Debt Securities	690,051	132,929
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	390,451	296,492
Unrealized Loss, Less than 12 months	13,082	2,241
Fair Value, Greater than 12 months	0	0
Unrealized Loss, Greater than 12 months	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	390,451	296,492
Unrealized Loss on AFS Debt Securities	13,082	2,241
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	29,665	0
Unrealized Loss, Less than 12 months	1,281	0
Fair Value, Greater than 12 months	16,725	18,899
Unrealized Loss, Greater than 12 months	3,094	919
Debt Securities, Available-for-sale, Unrealized Loss Position	46,390	18,899
Unrealized Loss on AFS Debt Securities	4,375	919
State and Municipal Obligations
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	1,204,526	876,691
Unrealized Loss, Less than 12 months	80,379	15,874
Fair Value, Greater than 12 months	136,076	32,684
Unrealized Loss, Greater than 12 months	15,435	1,049
Debt Securities, Available-for-sale, Unrealized Loss Position	1,340,602	909,375
Unrealized Loss on AFS Debt Securities	95,814	16,923
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	4,009,914	3,333,691
Unrealized Loss, Less than 12 months	242,976	59,044
Fair Value, Greater than 12 months	987,082	265,835
Unrealized Loss, Greater than 12 months	96,265	8,720
Debt Securities, Available-for-sale, Unrealized Loss Position	4,996,996	3,599,526
Unrealized Loss on AFS Debt Securities	339,241	67,764
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	1,360,220	1,285,611
Unrealized Loss, Less than 12 months	87,585	17,222
Fair Value, Greater than 12 months	28,932	1,948
Unrealized Loss, Greater than 12 months	2,525	19
Debt Securities, Available-for-sale, Unrealized Loss Position	1,389,152	1,287,559
Unrealized Loss on AFS Debt Securities	90,110	17,241
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	3,439,877	2,518,935
Unrealized Loss, Less than 12 months	106,785	19,201
Fair Value, Greater than 12 months	149,894	87,893
Unrealized Loss, Greater than 12 months	6,339	525
Debt Securities, Available-for-sale, Unrealized Loss Position	3,589,771	2,606,828
Unrealized Loss on AFS Debt Securities	113,124	19,726
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	8,810,011	7,138,237
Unrealized Loss, Less than 12 months	437,346	95,467
Fair Value, Greater than 12 months	1,165,908	355,676
Unrealized Loss, Greater than 12 months	105,129	9,264
Debt Securities, Available-for-sale, Unrealized Loss Position	9,975,919	7,493,913
Unrealized Loss on AFS Debt Securities	542,475	104,731
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	326,917	270,409
Unrealized Loss, Less than 12 months	17,622	5,098
Fair Value, Greater than 12 months	148,487	58,574
Unrealized Loss, Greater than 12 months	16,683	3,017
Debt Securities, Available-for-sale, Unrealized Loss Position	475,404	328,983
Unrealized Loss on AFS Debt Securities	$ 34,305	$ 8,115