Deferred Policy Acquisition Costs (Balance of and Changes in DAC) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 4,455,683		$ 4,447,505	$ 4,596,565
Capitalization of commissions, sales and issue expenses	339,151		412,627	372,996
Amortization-Impact of assumption and experience unlocking and true-ups	169,731		245,276	(113,534)
Amortization-All other	(573,745)		(518,129)	(476,261)
Change due to unrealized investment gains and losses	(154,488)		(131,596)	67,739
Other	1,448		0	0
Balance, end of year	$ 4,237,780	[1]	$ 4,455,683	$ 4,447,505

[1] December 31, 2020 amounts include the impacts of the January 1, 2020 adoption of ASU 2016-13. See Note 2 for details.