Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 8,435,531	$ 8,602,599
Available For Sale Securities, Gross Unreailzed Gain at Period End	148,959	35,266
Available For Sale Securities, Gross Unrealized Loss at Period End	(12,864)	(99,824)
Debt Securities, Available-for-sale, Fair Value	8,571,626	8,538,041
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	827,861	914,486
Available For Sale Securities, Gross Unreailzed Gain at Period End	23,957	4,545
Available For Sale Securities, Gross Unrealized Loss at Period End	(42)	(11,379)
Debt Securities, Available-for-sale, Fair Value	851,776	907,652
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	138,734	199,470
Available For Sale Securities, Gross Unreailzed Gain at Period End	730	55
Available For Sale Securities, Gross Unrealized Loss at Period End	(187)	(3,747)
Debt Securities, Available-for-sale, Fair Value	139,277	195,778
State and municipal obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,225,532	1,322,785
Available For Sale Securities, Gross Unreailzed Gain at Period End	42,427	10,284
Available For Sale Securities, Gross Unrealized Loss at Period End	(32)	(5,030)
Debt Securities, Available-for-sale, Fair Value	1,267,927	1,328,039
Agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,893,247	3,253,433
Available For Sale Securities, Gross Unreailzed Gain at Period End	50,890	9,820
Available For Sale Securities, Gross Unrealized Loss at Period End	(6,173)	(48,268)
Debt Securities, Available-for-sale, Fair Value	3,937,964	3,214,985
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	796,451	1,053,854
Available For Sale Securities, Gross Unreailzed Gain at Period End	14,036	6,641
Available For Sale Securities, Gross Unrealized Loss at Period End	(705)	(12,779)
Debt Securities, Available-for-sale, Fair Value	809,782	1,047,716
Asset-backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,228,151	1,518,976
Available For Sale Securities, Gross Unreailzed Gain at Period End	11,056	3,849
Available For Sale Securities, Gross Unrealized Loss at Period End	(5,718)	(11,211)
Debt Securities, Available-for-sale, Fair Value	1,233,489	1,511,614
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	5,917,849	5,826,263
Available For Sale Securities, Gross Unreailzed Gain at Period End	75,982	20,310
Available For Sale Securities, Gross Unrealized Loss at Period End	(12,596)	(72,258)
Debt Securities, Available-for-sale, Fair Value	5,981,235	5,774,315
Other Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	325,555	339,595
Available For Sale Securities, Gross Unreailzed Gain at Period End	5,863	72
Available For Sale Securities, Gross Unrealized Loss at Period End	(7)	(7,410)
Debt Securities, Available-for-sale, Fair Value	$ 331,411	$ 332,257

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.

No definition available.

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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.

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- References

No definition available.

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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=118939692&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=118942338&loc=SL82898722-210454

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- Definition

Amount 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 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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