Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 1,376,211	$ 1,341,093	$ 5,129,931
Capitalization of commissions, sales and issue expenses	346,885	278,892	316,828
Amortization-Impact of assumption and experience unlocking and true-ups	(54,772)	(16,140)	130,652
Amortization-All other	(81,054)	(78,867)	(758,753)
Change in unrealized investment gains and losses	26,652	(5,363)	(28,723)
Other	0	(143,404)	(3,448,842)
Balance, end of year	$ 1,613,922	$ 1,376,211	$ 1,341,093