Closed Block (Revenues and Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Premiums	$ 1,736	$ 1,804	$ 1,850
Net investment income	1,818	1,902	1,982
Net investment gains (losses)	1	(10)	(23)
Net derivative gains (losses)	(32)	25	27
Total revenues	3,523	3,721	3,836
Expenses
Policyholder benefits and claims	2,453	2,563	2,564
Policyholder dividends	976	953	1,015
Other expenses	125	133	143
Total expenses	3,554	3,649	3,722
Revenues, net of expenses before provision for income tax expense (benefit)	(31)	72	114
Provision for income tax expense (benefit)	12	24	41
Revenues, net of expenses and provision for income tax expense (benefit)	$ (43)	$ 48	$ 73