Consolidated Supplementary Insurance Information (Income Statement Items) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	$ 3,984	$ 4,277	$ 4,930
Net Investment Income	2,973	3,111	3,001
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	4,670	4,869	4,311
Amortization of DAC and VOBA Charged to Other Expenses	916	(225)	673
Other Expenses	1,833	1,700	1,723
Annuities
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	2,448	2,714	3,282
Net Investment Income	1,238	1,324	1,141
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	2,140	2,340	2,285
Amortization of DAC and VOBA Charged to Other Expenses	141	(908)	432
Other Expenses	1,035	903	938
Life
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	713	546	555
Net Investment Income	285	330	295
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	681	541	507
Amortization of DAC and VOBA Charged to Other Expenses	186	261	150
Other Expenses	237	242	259
Run-off
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	715	878	793
Net Investment Income	1,358	1,311	1,461
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	1,788	1,901	1,301
Amortization of DAC and VOBA Charged to Other Expenses	570	399	67
Other Expenses	278	275	285
Corporate & Other
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Universal Life and Investment-Type Product Policy Fees	108	139	300
Net Investment Income	92	146	104
Policyholder Benefits and Claims and Interest Credited to Policyholder Account Balances	61	87	218
Amortization of DAC and VOBA Charged to Other Expenses	19	23	24
Other Expenses	$ 283	$ 280	$ 241