Significant Accounting Policies (Details 4) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Summary of changes in accumulated other comprehensive income [Roll Forward]
Beginning balance accumulated other comprehensive income	$ 29,000,000		$ 17,784,000		$ 21,080,000		$ 12,480,000
Unrealized (losses) gains on securities, net of tax	(4,456,000)	[1]	9,202,000	[1]	3,806,000	[1]	15,669,000	[1]
Amounts reclassified from accumulated other comprehensive income	175,000		0		(167,000)		(1,163,000)
Net current period other comprehensive income	(4,281,000)		9,202,000		3,639,000		14,506,000
Ending balance accumulated other comprehensive income	24,719,000		26,986,000		24,719,000		26,986,000
Income tax expense included in other comprehensive income	$ (2,900,000)		$ 6,300,000		$ 2,500,000		$ 10,000,000

[1] Other comprehensive income for the three and six months ended June 30, 2014 includes income tax benefit of $2.9 million and income tax expense of $2.5 million, respectively, compared to an income tax benefit of $2.9 million and $10.0 million for the same periods in 2013.