Securities (Securities Available for Sale with Unrealized Losses) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	$ 842,011	$ 1,857,312
Available for sale, Losses less than 12 months, Gross Unrealized Losses	6,319	56,218
Available for sale, Losses 12 months or longer, Fair Value	1,569,320	3,738
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	39,099	69
Available for sale, Total, Fair Value	2,411,331	1,861,050
Available for sale, Total, Gross Unrealized Losses	45,418	56,287
U.S. Treasury And Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	45,616	54,788
Available for sale, Losses less than 12 months, Gross Unrealized Losses	42	1,923
Available for sale, Losses 12 months or longer, Fair Value	51,157
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	2,221
Available for sale, Total, Fair Value	96,773	54,788
Available for sale, Total, Gross Unrealized Losses	2,263	1,923
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	2,768	228,588
Available for sale, Losses less than 12 months, Gross Unrealized Losses	11	11,186
Available for sale, Losses 12 months or longer, Fair Value	173,530
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	3,335
Available for sale, Total, Fair Value	176,298	228,588
Available for sale, Total, Gross Unrealized Losses	3,346	11,186
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	461,835	1,087,644
Available for sale, Losses less than 12 months, Gross Unrealized Losses	4,195	19,359
Available for sale, Losses 12 months or longer, Fair Value	898,099	3,738
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	16,192	69
Available for sale, Total, Fair Value	1,359,934	1,091,382
Available for sale, Total, Gross Unrealized Losses	20,387	19,428
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	203,618	402,591
Available for sale, Losses less than 12 months, Gross Unrealized Losses	995	23,159
Available for sale, Losses 12 months or longer, Fair Value	411,046
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	16,868
Available for sale, Total, Fair Value	614,664	402,591
Available for sale, Total, Gross Unrealized Losses	17,863	23,159
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale, Losses less than 12 months, Fair Value	128,174	83,701
Available for sale, Losses less than 12 months, Gross Unrealized Losses	1,076	591
Available for sale, Losses 12 months or longer, Fair Value	35,488
Available for sale, Losses 12 months or longer, Gross Unrealized Losses	483
Available for sale, Total, Fair Value	163,662	83,701
Available for sale, Total, Gross Unrealized Losses	$ 1,559	$ 591

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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