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Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
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Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | $ 12,097,533,000 | $ 8,435,531,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 358,089,000 | 148,959,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (6,358,000) | (12,864,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Fair Value | 12,449,264,000 | 8,571,626,000
U.S. Government And Federal Agency Obligations [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 775,592,000 | 827,861,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 62,467,000 | 23,957,000
Available For Sale Securities, Gross Unrealized Loss at Period End | 0 | (42,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 838,059,000 | 851,776,000
US Government-sponsored Enterprise Debt Securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 50,803,000 | 138,734,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 3,780,000 | 730,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (98,000) | (187,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 54,485,000 | 139,277,000
State and municipal obligations [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 1,968,006,000 | 1,225,532,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 77,323,000 | 42,427,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (230,000) | (32,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 2,045,099,000 | 1,267,927,000
Agency mortgage-backed securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 6,557,098,000 | 3,893,247,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 157,789,000 | 50,890,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (2,802,000) | (6,173,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 6,712,085,000 | 3,937,964,000
Non-agency mortgage-backed securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 358,074,000 | 796,451,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 3,380,000 | 14,036,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (380,000) | (705,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 361,074,000 | 809,782,000
Asset-backed Securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 1,853,791,000 | 1,228,151,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 31,125,000 | 11,056,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (2,673,000) | (5,718,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 1,882,243,000 | 1,233,489,000
Total mortgage and asset-backed securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 8,768,963,000 | 5,917,849,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 192,294,000 | 75,982,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (5,855,000) | (12,596,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | 8,955,402,000 | 5,981,235,000
Other Debt Securities [Member] |  |
Investment [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 534,169,000 | 325,555,000
Available For Sale Securities, Gross Unreailzed Gain at Period End | 22,225,000 | 5,863,000
Available For Sale Securities, Gross Unrealized Loss at Period End | (175,000) | (7,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 |
Debt Securities, Available-for-sale, Fair Value | $ 556,219,000 | $ 331,411,000

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- Definition This item represents the gross unrealized gains for securities which are categorized as neither held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity. This concept represents the balance in unrealized gains at period-end. + References No definition available. + Details
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- Definition This item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity. This concept represents the balance in unrealized loss at period end. + References No definition available. + Details
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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details
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- Definition Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aaa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details
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