Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net earnings		$ 352,166	$ 299,619	$ 168,905
arising during the year		(27,392)	6,490	54,918
arising during the year		11,148	(2,869)	(22,317)
Unrealized net holding (losses) gains on securities available-for-sale, net of tax		(16,244)	3,621	32,601
Reclassification adjustment for net gains included in net earnings (1)	[1]	(9,485)	(3,744)	(4,841)
Income tax expense related to reclassification adjustment		3,883	1,571	1,967
Reclassification adjustment for net gains included in net earnings, net of tax		(5,602)	(2,173)	(2,874)
Other comprehensive (loss) income, net of tax		(21,846)	1,448	29,727
Comprehensive income		$ 330,320	$ 301,067	$ 198,632

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