Certain Long-Duration Contracts with Guarantees Liabilities for Guarantee Benefits (Details) - Variable Annuity Contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	$ 3,413,818	$ 3,387,128	$ 989,375
Incurred guarantee benefits	(1,939,713)	60,217	2,424,215
Paid guarantee benefits	(57,813)	(29,751)	(26,633)
Changes in unrealized investment gains and losses	(5,415)	(3,776)	171
Assumed guarantees upon reinsurance agreement with Pruco Life	6,971,668
Ending balance	8,382,545	3,413,818	3,387,128
GMDB
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	265,877	255,613	199,870
Incurred guarantee benefits	43,185	43,167	81,524
Paid guarantee benefits	(55,604)	(29,240)	(25,909)
Changes in unrealized investment gains and losses	(5,206)	(3,663)	128
Assumed guarantees upon reinsurance agreement with Pruco Life	389,067
Ending balance	637,319	265,877	255,613
GMAB/GMWB/ GMIWB
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	3,134,077	3,112,411	778,226
Incurred guarantee benefits	(1,979,215)	21,666	2,334,185
Paid guarantee benefits	0	0	0
Changes in unrealized investment gains and losses	0	0	0
Assumed guarantees upon reinsurance agreement with Pruco Life	6,552,471
Ending balance	7,707,333	3,134,077	3,112,411
GMIB
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	13,864	19,104	11,279
Incurred guarantee benefits	(3,683)	(4,616)	8,506
Paid guarantee benefits	(2,209)	(511)	(724)
Changes in unrealized investment gains and losses	(209)	(113)	43
Assumed guarantees upon reinsurance agreement with Pruco Life	30,130
Ending balance	$ 37,893	$ 13,864	$ 19,104