Accumulated Other Compensation Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended						6 Months Ended
	Jun. 30, 2014		Mar. 31, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income [Abstract]
Net income	$ 10,555		$ 25,080		$ 4,349		$ 35,635		$ 17,843
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	23,011		22,291		(48,189)		45,302		(54,599)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	9,663		9,363		(20,240)		19,026		(22,932)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	89	[1]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax			4,752	[1]	0	[1]	4,841	[1]	409	[1]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	37		1,996		0		2,033		172
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	13,296		10,172		(27,949)		23,468		(31,904)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 23,851		$ 35,252		$ (23,600)		$ 59,103		$ (14,061)

[1] (1) Recognized in "Gain on securities" on the Condensed Consolidated Statements of Earnings.