Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net earnings		$ 465,339	$ 357,818	$ 352,166
arising during the year		(52,559)	42,190	(27,392)
arising during the year		15,015	(17,481)	11,148
Unrealized net holding (losses) gains on securities available-for-sale, net of tax		(37,544)	24,709	(16,244)
Reclassification adjustment for net (gains) losses included in net earnings (1)	[1]	(8,176)	541	(9,485)
Income tax expense (benefit) related to reclassification adjustment		2,338	(61)	3,883
net of tax		(5,838)	480	(5,602)
Other comprehensive (loss) income, net of tax		(43,382)	25,189	(21,846)
Comprehensive income		$ 421,957	$ 383,007	$ 330,320

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