Securities (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
A roll-forward of the other-than-temporary impairment amount related to credit losses
Balance of credit losses on debt securities for which a portion of other-than-temporary impairment was recognized in other comprehensive income, beginning of period	$ 3,656	$ 1,415	$ 4,054
Additional credit loss for which other-than-temporary impairment was not previously recognized		868
Additional credit loss for which other-than-temporary impairment was previously recognized	398	1,373
Balance of credit losses on debt securities for which a portion of other-than-temporary impairment was recognized in other comprehensive income, end of period	$ 4,054	$ 3,656	$ 4,054