Fair Value Measurements, Level 3 Unobservable Inputs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reconciliation of assets and liabilities measured at fair value using significant unobservable inputs (Level 3) [Roll Forward]
Beginning balance, at fair value	$ 2,773	$ 2,933
OTTI impairment losses	(19)	(91)
Sales and principal payments	(133)	(131)
Change in unrealized loss	76	266
Ending balance, at fair value	$ 2,697	$ 2,977