Securities (Amortized Cost and Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	$ 2,879,343	$ 2,562,000
Securities Available for Sale, Gross Unrealized Gains	10,947	11,195
Securities Available for Sale, Gross Unrealized Losses	35,012	56,287
Securities Available for Sale, Fair Value	2,855,278	2,516,908
U.S. Treasury And Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	75,019	56,751
Securities Available for Sale, Gross Unrealized Gains	29
Securities Available for Sale, Gross Unrealized Losses	1,606	1,923
Securities Available for Sale, Fair Value	73,442	54,828
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	246,805	253,228
Securities Available for Sale, Gross Unrealized Gains	534	113
Securities Available for Sale, Gross Unrealized Losses	4,661	11,186
Securities Available for Sale, Fair Value	242,678	242,155
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	1,795,397	1,620,191
Securities Available for Sale, Gross Unrealized Gains	9,701	10,592
Securities Available for Sale, Gross Unrealized Losses	11,672	19,428
Securities Available for Sale, Fair Value	1,793,426	1,611,355
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	584,503	425,750
Securities Available for Sale, Gross Unrealized Gains	569
Securities Available for Sale, Gross Unrealized Losses	16,719	23,159
Securities Available for Sale, Fair Value	568,353	402,591
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	174,119	202,580
Securities Available for Sale, Gross Unrealized Gains	114	490
Securities Available for Sale, Gross Unrealized Losses	354	591
Securities Available for Sale, Fair Value	173,879	202,479
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	3,500	3,500
Securities Available for Sale, Fair Value	$ 3,500	$ 3,500

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: 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=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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