Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net earnings (loss)		$ (1,237,574)	$ 468,636	$ 465,339
arising during the year		142,696	143,019	(52,559)
(losses) arising during the year		(39,335)	(40,058)	15,015
net of tax		103,361	102,961	(37,544)
Reclassification adjustment for net (gains) losses included in net earnings (1)	[1]	(13,171)	(25,445)	(8,176)
Income tax expense (benefit) related to reclassification adjustment		3,675	7,217	2,338
net earnings, net of tax		(9,496)	(18,228)	(5,838)
Other comprehensive income (loss), net of tax		93,865	84,733	(43,382)
Comprehensive income (loss)		$ (1,143,709)	$ 553,369	$ 421,957

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