Accumulative Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Components of accumulated other comprehensive income (loss)
Net unrealized gain (loss) on available-for-sale securities	$ 42		$ (1,261)
Accumulated Other Comprehensive Income (Loss)	$ 42	$ 74	$ (1,261)	$ (2,011)