Securities Available-for-Sale (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
U.S. Government Sponsored Enterprises [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value	$ 29,883	$ 34,967
Less than 12 months, Unrealized Losses	117	68
Total, Fair Value	29,883	34,967
Total, Unrealized Losses	117	68
U.S. Government Agency and Sponsored Enterprise Mortgage Backed Securities [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value	283,816	93,006
Less than 12 months, Unrealized Losses	1,589	383
12 months or longer, Fair Value	2,834	10,169
12 months or longer, Unrealized Losses	24	29
Total, Fair Value	286,650	103,175
Total, Unrealized Losses	1,613	412
Privately Issued Residential Mortgage Backed Securities [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value	781
Less than 12 months, Unrealized Losses	1
12 months or longer, Fair Value	1,017	1,863
12 months or longer, Unrealized Losses	15	22
Total, Fair Value	1,798	1,863
Total, Unrealized Losses	16	22
Obligations Issued by States and Political Subdivisions [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value
Less than 12 months, Unrealized Losses
12 months or longer, Fair Value	3,963	3,963
12 months or longer, Unrealized Losses	723	722
Total, Fair Value	3,963	3,963
Total, Unrealized Losses	723	722
Other Debt Securities [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value
Less than 12 months, Unrealized Losses
12 months or longer, Fair Value	1,439	1,453
12 months or longer, Unrealized Losses	62	47
Total, Fair Value	1,439	1,453
Total, Unrealized Losses	62	47
Equity Securities [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value
Less than 12 months, Unrealized Losses
12 months or longer, Fair Value
12 months or longer, Unrealized Losses
Total, Fair Value
Total, Unrealized Losses
Total Temporarily Impaired Investment [Member]
Continuous unrealized loss position for 12 months or less and 12 months or longer
Less than 12 months, Fair Value	314,480	127,973
Less than 12 months, Unrealized Losses	1,707	451
12 months or longer, Fair Value	9,253	17,448
12 months or longer, Unrealized Losses	824	820
Total, Fair Value	323,733	145,421
Total, Unrealized Losses	$ 2,531	$ 1,271