Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,087,069	$ 1,680,491
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	25,527	22,551
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(14,339)	(38,931)
Securities available for sale	2,098,257us-gaap_AvailableForSaleSecurities	1,664,111us-gaap_AvailableForSaleSecurities
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Available-for-sale Securities, Gross Realized Losses	1	170	714
Available-for-sale Securities, Gross Realized Gains	553	632	4,447
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	1,160,378	961,442
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10,219	10,640
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(8,210)	(23,674)
Securities available for sale	1,162,387	948,408
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	483,578	357,013
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	14,432	11,450
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,526)	(3,993)
Securities available for sale	496,484	364,470
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	416,919	335,671
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	856	434
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(4,069)	(10,066)
Securities available for sale	413,706	326,039
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,910	21,081
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(411)	(967)
Securities available for sale	20,499	20,114
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	20	27
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(123)	(231)
Securities available for sale	$ 5,181	$ 5,080

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

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