Securities (Amortized Cost and Fair Value of Securities Held to Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	$ 2,896,442	$ 2,979,547
Securities Held to Maturity, Gross Unrealized Gains	19,466	5,782
Securities Held to Maturity, Gross Unrealized Losses	22,998	49,473
Securities Held to Maturity, Fair Value	2,892,910	2,935,856
U.S. Treasury And Government Agency Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	50,000	50,000
Securities Held to Maturity, Gross Unrealized Losses	317	478
Securities Held to Maturity, Fair Value	49,683	49,522
Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	676,651	688,201
Securities Held to Maturity, Gross Unrealized Gains	11,247	2,347
Securities Held to Maturity, Gross Unrealized Losses	1,726	9,503
Securities Held to Maturity, Fair Value	686,172	681,045
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	613,964	640,393
Securities Held to Maturity, Gross Unrealized Gains	3,701	1,461
Securities Held to Maturity, Gross Unrealized Losses	3,148	6,117
Securities Held to Maturity, Fair Value	614,517	635,737
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	356,919	357,175
Securities Held to Maturity, Gross Unrealized Gains	1,233	376
Securities Held to Maturity, Gross Unrealized Losses	3,780	10,882
Securities Held to Maturity, Fair Value	354,372	346,669
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Amortized Cost	1,198,908	1,243,778
Securities Held to Maturity, Gross Unrealized Gains	3,285	1,598
Securities Held to Maturity, Gross Unrealized Losses	14,027	22,493
Securities Held to Maturity, Fair Value	$ 1,188,166	$ 1,222,883

Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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- Definition

Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

+ References

+ Details

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- Definition

Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

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- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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