Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net earnings		$ 85,083	$ 73,079	$ 10,555	$ 158,162	$ 35,635
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Unrealized holding (losses) gains on securities available-for-sale		(21,213)	7,363	23,011	(13,850)	45,302
Income tax benefit (expense) related to unrealized holding (losses) gains arising during the period		8,614	(3,105)	(9,663)	5,509	(19,026)
Unrealized holding losses (gains) on securities available-for-sale, net of tax		(12,599)	4,258	13,348	(8,341)	26,276
Reclassification adjustment for losses (gains) included in net earnings	[1]	186	(3,275)	(89)	(3,089)	(4,841)
Income tax (benefit) expense related to reclassification adjustment		(76)	1,381	37	1,305	2,033
Reclassification adjustment for losses (gains) included in net earnings, net of tax		110	(1,894)	(52)	(1,784)	(2,808)
Other comprehensive (loss) income, net of tax		(12,489)	2,364	13,296	(10,125)	23,468
Comprehensive income		$ 72,594	$ 75,443	$ 23,851	$ 148,037	$ 59,103

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