Securities (Securities Available for Sale with Unrealized Losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available for Sale, Losses less than 12 months, Fair Value	$ 1,835,939	$ 1,857,312
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	53,934	56,218
Available for Sale, Losses 12 months or longer, Fair Value	3,110	3,738
Available for Sale, Losses 12 months or longer, Gross Unrealized Losses	76	69
Available for Sale, Total, Fair Value	1,839,049	1,861,050
Available for Sale, Total, Gross Unrealized Losses	54,010	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	74,460	54,788
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	1,553	1,923
Available for Sale, Total, Fair Value	74,460	54,788
Available for Sale, Total, Gross Unrealized Losses	1,553	1,923
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale, Losses less than 12 months, Fair Value	228,433	228,588
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	10,537	11,186
Available for Sale, Total, Fair Value	228,433	228,588
Available for Sale, Total, Gross Unrealized Losses	10,537	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	1,051,706	1,087,644
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	18,885	19,359
Available for Sale, Losses 12 months or longer, Fair Value	3,110	3,738
Available for Sale, Losses 12 months or longer, Gross Unrealized Losses	76	69
Available for Sale, Total, Fair Value	1,054,816	1,091,382
Available for Sale, Total, Gross Unrealized Losses	18,961	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	403,123	402,591
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	22,360	23,159
Available for Sale, Total, Fair Value	403,123	402,591
Available for Sale, Total, Gross Unrealized Losses	22,360	23,159
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for Sale, Losses less than 12 months, Fair Value	78,217	83,701
Available for Sale, Losses less than 12 months, Gross Unrealized Losses	599	591
Available for Sale, Total, Fair Value	78,217	83,701
Available for Sale, Total, Gross Unrealized Losses	$ 599	$ 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
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-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

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