Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($)	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 10,097,801,000	$ 10,127,426,000
Fair Value	9,264,947,000	9,136,853,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,626,515,000	2,594,130,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost	437,727,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	1,449,802,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost	738,986,000
Fair Value	2,626,635,000	2,555,252,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value	438,583,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value	1,451,299,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value	736,753,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,041,000	55,425,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost	35,221,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost	19,820,000
Fair Value	44,056,000	42,849,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value	30,150,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	13,906,000
State and municipal obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	789,579,000	822,790,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost	69,962,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	400,964,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost	205,286,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost	113,367,000
Fair Value	721,187,000	742,891,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value	69,275,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value	376,308,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value	179,376,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	96,228,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,098,966,000	4,195,182,000
Fair Value	3,430,566,000	3,444,891,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	614,798,000	625,539,000
Fair Value	566,126,000	568,689,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,652,018,000	1,595,797,000
Fair Value	1,625,282,000	1,557,015,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,365,782,000	6,416,518,000
Fair Value	5,621,974,000	5,570,595,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	260,884,000	238,563,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost	64,955,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	68,308,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost	102,874,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost	24,747,000
Fair Value	251,095,000	$ 225,266,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value	64,330,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value	63,659,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value	98,777,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	$ 24,329,000