Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,299,037	$ 2,157,610
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10,231	18,352
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(30,691)	(18,268)
Securities available for sale	2,278,577	2,157,694
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Available-for-sale Securities, Gross Realized Losses	0	10	$ 1
Available-for-sale Securities, Gross Realized Gains	1,181	1,591	$ 553
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,486,690	1,296,955
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,760	4,525
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(23,718)	(14,991)
Securities available for sale	1,465,732	1,286,489
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	473,914	480,417
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	6,343	12,690
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(5,197)	(938)
Securities available for sale	475,060	492,169
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	332,348	354,515
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,065	1,113
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,511)	(1,846)
Securities available for sale	331,902	353,782
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	801	20,439
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1)	(302)
Securities available for sale	800	20,137
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,284	5,284
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	63	24
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(264)	(191)
Securities available for sale	$ 5,083	$ 5,117

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
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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