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	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 612,600	$ 571,058
Gross Unrealized Gains	7,902	16,739
Gross Unrealized Losses	(11,849)	(195)
Fair Value	608,653	587,602
U.S. Treasury and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,754	23,570
Gross Unrealized Gains	2	40
Gross Unrealized Losses	(969)	(138)
Fair Value	19,787	23,472
Obligations of State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	95,033	71,352
Gross Unrealized Gains	2,793	5,145
Gross Unrealized Losses	(555)	(12)
Fair Value	97,271	76,485
Mortgage-backed Securities - Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	496,129	475,452
Gross Unrealized Gains	4,765	11,505
Gross Unrealized Losses	(10,325)	(45)
Fair Value	490,569	486,912
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	684	684
Gross Unrealized Gains	342	49
Gross Unrealized Losses	0	0
Fair Value	$ 1,026	$ 733