Securities (Amortized Cost and Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	$ 2,949,057	$ 2,562,000
Securities Available for Sale, Gross Unrealized Gains	7,230	11,195
Securities Available for Sale, Gross Unrealized Losses	45,418	56,287
Securities Available for Sale, Fair Value	2,910,869	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	99,535	56,751
Securities Available for Sale, Gross Unrealized Losses	2,263	1,923
Securities Available for Sale, Fair Value	97,272	54,828
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	245,997	253,228
Securities Available for Sale, Gross Unrealized Gains	1,135	113
Securities Available for Sale, Gross Unrealized Losses	3,346	11,186
Securities Available for Sale, Fair Value	243,786	242,155
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	1,729,989	1,620,191
Securities Available for Sale, Gross Unrealized Gains	5,611	10,592
Securities Available for Sale, Gross Unrealized Losses	20,387	19,428
Securities Available for Sale, Fair Value	1,715,213	1,611,355
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	704,518	425,750
Securities Available for Sale, Gross Unrealized Gains	480
Securities Available for Sale, Gross Unrealized Losses	17,863	23,159
Securities Available for Sale, Fair Value	687,135	402,591
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Amortized Cost	165,518	202,580
Securities Available for Sale, Gross Unrealized Gains	4	490
Securities Available for Sale, Gross Unrealized Losses	1,559	591
Securities Available for Sale, Fair Value	163,963	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
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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
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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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