Securities, Available-for-sale (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	$ 247,915	$ 142,581
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	3,239	1,176
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	247,915	142,581
Total Investments with an Unrealized Loss, Unrealized Losses	3,239	1,176
U.S. Government Agency Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	121,169	78,899
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	1,420	414
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	121,169	78,899
Total Investments with an Unrealized Loss, Unrealized Losses	1,420	414
Mortgage-backed Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	67,940	40,988
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	1,595	623
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	67,940	40,988
Total Investments with an Unrealized Loss, Unrealized Losses	1,595	623
State and Municipal Securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	41,084	5,179
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	187	126
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	41,084	5,179
Total Investments with an Unrealized Loss, Unrealized Losses	187	126
Agency-backed securities [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	17,358	17,353
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	35	9
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	17,358	17,353
Total Investments with an Unrealized Loss, Unrealized Losses	35	9
Corporate Notes [Member]
Available-for-sale securities, continuous unrealized loss position [Abstract]
Investments with an Unrealized Loss of less than 12 months, Fair Value	364	162
Investments with an Unrealized Loss of less than 12 months, Unrealized Losses	2	4
Investments with an Unrealized Loss of 12 months or longer, Fair Value	0	0
Investments with an Unrealized Loss of 12 months or longer, Unrealized Losses	0	0
Total Investments with an Unrealized Loss, Fair Value	364	162
Total Investments with an Unrealized Loss, Unrealized Losses	$ 2	$ 4