Securities (Amortized Cost, Unrealized Gross Gains and Losses Recognized in Accumulated Other Comprehensive Income (Loss), and Fair Value of Securities Available-for-Sale) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 614,402	$ 571,058
Gross Unrealized Gains	8,311	16,739
Gross Unrealized Losses	(10,144)	(195)
Fair Value	612,569	587,602
U.S. Treasury and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,257	23,570
Gross Unrealized Gains	22	40
Gross Unrealized Losses	(918)	(138)
Fair Value	22,361	23,472
Obligations of State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	76,710	71,352
Gross Unrealized Gains	2,585	5,145
Gross Unrealized Losses	(530)	(12)
Fair Value	78,765	76,485
Mortgage-backed Securities - Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	513,751	475,452
Gross Unrealized Gains	5,624	11,505
Gross Unrealized Losses	(8,696)	(45)
Fair Value	510,679	486,912
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	684	684
Gross Unrealized Gains	80	49
Gross Unrealized Losses	0	0
Fair Value	$ 764	$ 733