Reinsurance (Amounts included in the Statements of Operations and Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums
Direct	$ 8,028	$ 11,909	$ 26,216	$ 28,958
Assumed	5,849	(10,248)	25,402	821,089
Ceded	(1,372)	(2,256)	(2,952)	(2,554)
Net premiums	12,505	(595)	48,666	847,493
Policy charges and fee income
Direct	153,835	163,547	469,128	487,837
Assumed	413,400	392,156	1,210,789	766,451
Ceded	(11,328)	(11,522)	(33,607)	(34,582)
Net policy charges and fee income	555,907	544,181	1,646,310	1,219,706
Asset administration fees and other income
Direct	30,573	29,814	97,972	97,246
Assumed	74,586	69,493	216,697	135,902
Ceded	(2,446)	(2,502)	(7,285)	(7,316)
Net asset administration fees and other income	102,713	96,805	307,384	225,832
Realized investment gains (losses), net
Direct	(32,663)	(409,674)	(779,499)	507,527
Assumed	1,237,967	394,419	470,545	(3,366,784)
Ceded	(35,227)	(20,470)	(18,558)	361,596
Realized investment gains (losses), net	1,170,077	(35,725)	(327,512)	(2,497,661)
Policyholders' benefits (including change in reserves)
Direct	10,061	10,835	36,627	49,471
Assumed	6,114	(8,895)	28,505	526,292
Ceded	(2,119)	(10,873)	15,119	(21,417)
Net policyholders' benefits (including change in reserves)	14,056	(8,933)	80,251	554,346
Interest credited to policyholders’ account balances
Direct	42,401	(64,111)	(5,421)	87,752
Assumed	52,559	(27,278)	9,108	18,816
Ceded	(4,461)	5,774	(3,120)	(5,384)
Net interest credited to policyholders’ account balances	90,499	(85,615)	567	101,184
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	352,114	(14,625)	524,961	504,820
Unaffiliated activity
Policy charges and fee income
Ceded	(600)	(300)	(2,000)	(1,000)
Policyholders' benefits (including change in reserves)
Ceded	$ 0	$ 0	$ 0	$ (200)