Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net earnings		$ 299,619	$ 168,905	$ 45,115
Unrealized holding gains (losses) on securities available-for-sale arising during the year		6,490	54,918	(57,136)
Income tax (expense) benefit related to unrealized holding (losses) gains arising during the year		(2,869)	(22,317)	26,190
Unrealized holding gains (losses) on securities available-for-sale, net of tax		3,621	32,601	(30,946)
Reclassification adjustment for gains included in net earnings (1)	[1]	(3,744)	(4,841)	(5,359)
Income tax expense related to reclassification adjustment		1,571	1,967	58
Reclassification adjustment for gains included in net earnings, net of tax		(2,173)	(2,874)	(5,301)
Other comprehensive income (loss), net of tax		1,448	29,727	(36,247)
Comprehensive income		$ 301,067	$ 198,632	$ 8,868

[1] Entire amount recognized in "Gain on securities" on the Consolidated Statements of Earnings.