Certain Long-Duration Contracts with Guarantees (Sales Inducements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Deferred Sales Inducements [Roll Forward]
Beginning balance	$ 452,752	$ 665,207	$ 809,247
Capitalization	1,805	873	11,515
Amortization - Impact of assumption and experience unlocking and true-ups	101,424	21,125	45,417
Amortization - All other	(81,603)	(206,263)	(204,563)
Change in unrealized investment gains and losses	4,915	11,063	3,591
Ceded DSI upon Reinsurance Treaty with Prudential Insurance		(39,253)
Assumed DSI upon Reinsurance Treaty with Pruco Life Insurance Company	499,530
Ending balance	$ 978,823	$ 452,752	$ 665,207