Fair Value of Assets and Liabilities (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Security	Mar. 31, 2012	Dec. 31, 2012 Security
Breakdown of trust preferred securities
Life-to-date impairment recognized in earnings		$ 171
Life-to-date impairment recognized in other comprehensive income		136
Total life-to-date impairment		35
Trust preferred securities
Breakdown of trust preferred securities
Total number of trust preferred securities	12		12
Par value	14,449		14,449
Number not considered OTTI	10		10
Par value	11,491		11,491
Number considered OTTI	2		2
Par value	2,958		2,958
Life-to-date impairment recognized in earnings	351	171	351
Life-to-date impairment recognized in other comprehensive income	1,687	136	1,868
Total life-to-date impairment	$ 2,038		$ 2,219