Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 14,419,133,000	$ 12,097,533,000
Debt Securities, Available-for-sale, Fair Value		14,450,027,000	12,449,264,000
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1,035,477,000	775,592,000
Debt Securities, Available-for-sale, Fair Value		$ 1,080,720,000	838,059,000
Weighted Average Yield	[1]	1.34%
U.S. Government And Federal Agency Obligations [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 137,340,000
Debt Securities, Available-for-sale, Fair Value		$ 139,354,000
Weighted Average Yield	[1]	2.24%
U.S. Government And Federal Agency Obligations [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 698,147,000
Debt Securities, Available-for-sale, Fair Value		$ 715,106,000
Weighted Average Yield	[1]	1.35%
U.S. Government And Federal Agency Obligations [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 199,990,000
Debt Securities, Available-for-sale, Fair Value		$ 226,260,000
Weighted Average Yield	[1]	0.70%
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 50,773,000	50,803,000
Debt Securities, Available-for-sale, Fair Value		$ 51,755,000	54,485,000
Weighted Average Yield		2.32%
US Government-sponsored Enterprise Debt Securities [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 50,773,000
Debt Securities, Available-for-sale, Fair Value		$ 51,755,000
Weighted Average Yield		2.32%
State and municipal obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 2,072,210,000	1,968,006,000
Debt Securities, Available-for-sale, Fair Value		$ 2,096,827,000	2,045,099,000
Weighted Average Yield		1.97%
State and municipal obligations [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 164,524,000
Debt Securities, Available-for-sale, Fair Value		$ 166,146,000
Weighted Average Yield		2.34%
State and municipal obligations [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 763,794,000
Debt Securities, Available-for-sale, Fair Value		$ 786,416,000
Weighted Average Yield		2.11%
State and municipal obligations [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 773,513,000
Debt Securities, Available-for-sale, Fair Value		$ 780,313,000
Weighted Average Yield		1.79%
State and municipal obligations [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 370,379,000
Debt Securities, Available-for-sale, Fair Value		$ 363,952,000
Weighted Average Yield		1.88%
Agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 5,698,088,000	6,557,098,000
Debt Securities, Available-for-sale, Fair Value		$ 5,683,000,000	6,712,085,000
Weighted Average Yield		1.94%
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 1,383,037,000	358,074,000
Debt Securities, Available-for-sale, Fair Value		$ 1,366,477,000	361,074,000
Weighted Average Yield		1.84%
Asset-backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 3,546,024,000	1,853,791,000
Debt Securities, Available-for-sale, Fair Value		$ 3,539,219,000	1,882,243,000
Weighted Average Yield		1.05%
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 10,627,149,000	8,768,963,000
Debt Securities, Available-for-sale, Fair Value		$ 10,588,696,000	8,955,402,000
Weighted Average Yield		1.63%
Other Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 633,524,000	534,169,000
Debt Securities, Available-for-sale, Fair Value		$ 632,029,000	$ 556,219,000
Weighted Average Yield		1.97%
Other Debt Securities [Member] | Maturity Within 1 Year [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 126,406,000
Debt Securities, Available-for-sale, Fair Value		$ 127,604,000
Weighted Average Yield		2.68%
Other Debt Securities [Member] | Maturity After 1 But Within 5 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 191,083,000
Debt Securities, Available-for-sale, Fair Value		$ 193,429,000
Weighted Average Yield		1.87%
Other Debt Securities [Member] | Maturity After 5 But Within 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 306,775,000
Debt Securities, Available-for-sale, Fair Value		$ 301,854,000
Weighted Average Yield		1.74%
Other Debt Securities [Member] | Maturity After 10 Years [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		$ 9,260,000
Debt Securities, Available-for-sale, Fair Value		$ 9,142,000
Weighted Average Yield		1.89%

[1] Rate does not reflect inflation adjustment on inflation-protected securities