Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,157,610	$ 2,087,069
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	18,352	25,527
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(18,268)	(14,339)
Securities available for sale	2,157,694	2,098,257
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Available-for-sale Securities, Gross Realized Losses	10	1	$ 170
Available-for-sale Securities, Gross Realized Gains	1,591	553	$ 632
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	1,296,955	1,160,378
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	4,525	10,219
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(14,991)	(8,210)
Securities available for sale	1,286,489	1,162,387
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	480,417	483,578
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12,690	14,432
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(938)	(1,526)
Securities available for sale	492,169	496,484
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	354,515	416,919
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,113	856
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,846)	(4,069)
Securities available for sale	353,782	413,706
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,439	20,910
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(302)	(411)
Securities available for sale	20,137	20,499
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	24	20
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(191)	(123)
Securities available for sale	$ 5,117	$ 5,181

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=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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