Significant Accounting Policies (Details 4) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary of changes in accumulated other comprehensive income (loss)
Beginning balance accumulated other comprehensive income (loss)	$ 17,784,000	$ (242,000)	$ 12,480,000	$ (770,000)
Other comprehensive income before reclassifications, net of tax	9,202,000	1,210,000	15,669,000	1,738,000
Amounts reclassified from accumulated other comprehensive income			(1,163,000)
Net current period other comprehensive income	9,202,000	1,210,000	14,506,000	1,738,000
Ending balance accumulated other comprehensive income (loss)	26,986,000	968,000	26,986,000	968,000
Income tax expense included in other comprehensive income	$ 6,300,000		$ 10,000,000