Deferred Policy Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 4,344,361	$ 749,302	$ 1,114,431
Capitalization of commissions, sales and issue expenses	277,586	269,679	1,535
Amortization-Impact of assumption and experience unlocking and true-ups	288,974	226,204	33,113
Amortization-All other	(275,028)	(46,388)	(342,265)
Changes in unrealized investment gains and losses	(39,328)	18,772	16,352
Ceded DAC upon Reinsurance Treaty with Prudential Insurance	0	(7,480)	(73,864)
Assumed DAC upon Reinsurance Treaty with Pruco Life	0	3,134,272	0
Balance, end of year	$ 4,596,565	4,344,361	$ 749,302
True-up to the ceded DAC upon reinsurance agreement with Prudential Insurance		$ 7,500