Other Comprehensive Income (Loss), Summary of Unrealized Gains and Losses on Available-for-Sale Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss)	$ 962	$ (347)	$ 3,313	$ 4,824	$ (2,076)	$ (779)	$ (8,903)	$ (2,462)	$ 8,752	$ (14,220)	$ 503
Accumulated Net Unrealized Investment Gain (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of year				(6,591)				7,940	(6,591)	7,940	7,401
Unrealized gains (losses) arising during the period									15,175	(21,268)	2,797
Realized gains during the period									(1,155)	(1,087)	(1,968)
Related deferred taxes									(4,907)	7,824	(290)
Other comprehensive income (loss)									9,113	(14,531)	539
Balance at end of year	$ 2,522				$ (6,591)				$ 2,522	$ (6,591)	$ 7,940