Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 item	Mar. 31, 2013 item	Dec. 31, 2013
Securities available for sale
Securities available for sale, amortized cost	$ 440,104		$ 493,066
Unrealized gains	5,108		4,487
Unrealized losses	5,028		7,522
Total securities available for sale, fair value	440,184		490,031
Held to maturity securities	0		0
Number of securities sold	0	0
U.S. Treasury and other U.S. government obligations
Securities available for sale
Securities available for sale, amortized cost	40,000		110,000
Total securities available for sale, fair value	40,000		110,000
Government sponsored enterprise obligations
Securities available for sale
Securities available for sale, amortized cost	156,246		138,094
Unrealized gains	1,665		1,623
Unrealized losses	1,554		1,872
Total securities available for sale, fair value	156,357		137,845
Mortgage-backed securities - government agencies
Securities available for sale
Securities available for sale, amortized cost	175,020		176,524
Unrealized gains	1,523		1,391
Unrealized losses	3,263		5,222
Total securities available for sale, fair value	173,280		172,693
Obligations of states and political subdivisions
Securities available for sale
Securities available for sale, amortized cost	68,082		68,448
Unrealized gains	1,634		1,473
Unrealized losses	211		428
Total securities available for sale, fair value	69,505		69,493
Corporate equity securities
Securities available for sale
Securities available for sale, amortized cost	756
Unrealized gains	286
Total securities available for sale, fair value	$ 1,042