Significant Accounting Policies (Details 4) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Summary of changes in accumulated other comprehensive income (loss)
Beginning balance accumulated other comprehensive income (loss)	$ 12,480,000	$ (770,000)
Other comprehensive income before reclassifications, net of tax	6,467,000	528,000
Amounts reclassified from accumulated other comprehensive income	(1,163,000)
Net current period other comprehensive income	5,304,000	528,000
Ending balance accumulated other comprehensive income (loss)	17,784,000	(242,000)
Income tax expense included in other comprehensive income	$ 3,600,000