Reinsurance (Income Statement Reinsurance Results) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums:
Direct	$ 39,326	$ 33,250	$ 34,903
Assumed	860,831	0	0
Ceded	(3,318)	(23,463)	0
Net premiums	896,839	9,787	34,903
Policy charges and fee income:
Direct	647,226	743,956	809,072
Assumed	1,153,752	0	0
Ceded	(45,754)	(3,133)	(2,745)
Net policy charges and fee income	1,755,224	740,823	806,327
Asset administration fees and other income:
Direct	103,892	177,479	227,619
Assumed	205,221	0	0
Ceded	(9,729)	0	0
Net asset administration fees and other income	299,384	177,479	227,619
Realized investment gains (losses), net:
Direct	(3,612,578)	247,525	(1,967,588)
Assumed	(81,510)	0	0
Ceded	251,328	(241,473)	1,974,956
Total realized investment gains (losses), net	(3,442,760)	6,052	7,368
Policyholders' benefits (including change in reserves):
Direct	74,438	81,719	137,502
Assumed	553,280	0	0
Ceded	(23,661)	(21,258)	(367)
Net policyholders' benefits (including change in reserves)	604,057	60,461	137,135
Interest credited to policyholders’ account balances:
Direct	74,389	225,555	211,058
Assumed	(1,551)	0	0
Ceded	(3,949)	0	0
Net interest credited to policyholders’ account balances	68,889	225,555	211,058
Net reinsurance expense allowances, net of capitalization and amortization(3)	563,027	(6,054)	(3,874)
Unaffiliated activity
Policy charges and fee income:
Ceded	(2,000)	(3,000)	(3,000)
Policyholders' benefits (including change in reserves):
Ceded	$ (300)	$ (100)	$ (400)