Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net earnings		$ 69,616	$ 85,083	$ 62,271	$ 227,778	$ 97,906
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized holding (losses) gains on securities available-for-sale		14,466	(21,213)	93	616	45,395
Income tax benefit (expense) related to unrealized holding (losses) gains arising during the period		(5,873)	8,614	607	(364)	(18,342)
Unrealized holding losses (gains) on securities available-for-sale, net of tax		8,593	(12,599)	700	252	27,053
Reclassification adjustment for losses (gains) included in net earnings	[1]	(655)	186	0	(3,744)	(4,841)
Income tax (benefit) expense related to reclassification adjustment		266	(76)	0	1,571	1,956
Reclassification adjustment for losses (gains) included in net earnings, net of tax		(389)	110	0	(2,173)	(2,885)
Other comprehensive (loss) income, net of tax		8,204	(12,489)	700	(1,921)	24,168
Comprehensive income		$ 77,820	$ 72,594	$ 62,971	$ 225,857	$ 122,074

[1] Entire amounts are recognized in "Gain (loss) on sale of securities" on the Condensed Consolidated Statements of Earnings.