Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 4,447,505	$ 4,596,565	$ 4,344,361
Capitalization of commissions, sales and issue expenses	412,627	372,996	277,586
Amortization-Impact of assumption and experience unlocking and true-ups	245,276	(113,534)	288,974
Amortization-All other	(518,129)	(476,261)	(275,028)
Change in unrealized investment gains and losses	(131,596)	67,739	(39,328)
Balance, end of year	$ 4,455,683	$ 4,447,505	$ 4,596,565