Certain Long-Duration Contracts with Guarantees (Liabilities for Guarantee Benefits) (Details) - 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	$ 8,858,768	$ 8,276,441	$ 1,716,198
Incurred guarantee benefits	628,842	839,578	6,313,676
Paid guarantee benefits	(76,447)	(57,770)	(41,124)
Changes in unrealized investment gains and losses	103,057	(199,481)	287,691
Ending balance	9,514,220	8,858,768	8,276,441
GMDB | Variable Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	376,894	321,217	207,854
Incurred guarantee benefits	48,832	95,747	131,594
Paid guarantee benefits	(38,661)	(34,021)	(22,079)
Changes in unrealized investment gains and losses	928	(6,049)	3,848
Ending balance	387,993	376,894	321,217
GMDB | Variable Life, Variable Universal Life & Universal Life(2)
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	3,245,821	2,921,933	1,834,290
Incurred guarantee benefits	746,130	538,906	822,167
Paid guarantee benefits	(35,894)	(21,811)	(18,192)
Changes in unrealized investment gains and losses	102,124	(193,207)	283,668
Ending balance	4,058,181	3,245,821	2,921,933
GMIB | Variable Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	30,618	39,681	22,454
Incurred guarantee benefits	(1,693)	(6,900)	17,905
Paid guarantee benefits	(1,892)	(1,938)	(853)
Changes in unrealized investment gains and losses	5	(225)	175
Ending balance	27,038	30,618	39,681
GMWB/GMIWB/ GMAB | Variable Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	5,205,435	4,993,610	(348,400)
Incurred guarantee benefits	(164,427)	211,825	5,342,010
Paid guarantee benefits	0	0	0
Changes in unrealized investment gains and losses	0	0	0
Ending balance	$ 5,041,008	$ 5,205,435	$ 4,993,610