Fair Value (Financial Instruments Carried at Other Than Fair Value) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets
Policy loans	$ 9,585	$ 9,511
Liabilities
Collateral financing arrangements	1,220	1,274
Junior subordinated debt securities	3,144	3,169
Separate account liabilities	203,399	195,578
Carrying Value
Assets
Mortgage loans	67,493	64,601
Policy loans	9,585	9,511
Real estate joint ventures	2	4
Other limited partnership interests	239	340
Other invested assets	553	497
Premiums, reinsurance and other receivables	4,140	4,088
Other assets	272	237
Liabilities
Policyholder account balances	114,100	108,255
Long-term debt	16,676	16,422
Collateral financing arrangements	1,220	1,274
Junior subordinated debt securities	3,144	3,169
Other liabilities	5,122	1,767
Separate account liabilities	123,586	118,385
Estimated Fair Value
Assets
Mortgage loans	69,218	65,742
Policy loans	11,427	11,256
Real estate joint ventures	11	26
Other limited partnership interests	243	371
Other invested assets	553	497
Premiums, reinsurance and other receivables	4,333	4,279
Other assets	304	269
Liabilities
Policyholder account balances	116,637	110,359
Long-term debt	18,596	17,972
Collateral financing arrangements	945	978
Junior subordinated debt securities	4,337	3,982
Other liabilities	5,759	1,768
Separate account liabilities	123,586	118,385
Estimated Fair Value | Level 1
Assets
Mortgage loans	0	0
Policy loans	0	0
Real estate joint ventures	0	0
Other limited partnership interests	0	0
Other invested assets	159	145
Premiums, reinsurance and other receivables	0	0
Other assets	0	0
Liabilities
Policyholder account balances	0	0
Long-term debt	0	0
Collateral financing arrangements	0	0
Junior subordinated debt securities	0	0
Other liabilities	0	0
Separate account liabilities	0	0
Estimated Fair Value | Level 2
Assets
Mortgage loans	0	0
Policy loans	335	335
Real estate joint ventures	0	0
Other limited partnership interests	0	0
Other invested assets	0	0
Premiums, reinsurance and other receivables	1,244	1,152
Other assets	191	198
Liabilities
Policyholder account balances	0	0
Long-term debt	18,596	17,972
Collateral financing arrangements	0	0
Junior subordinated debt securities	4,337	3,982
Other liabilities	3,466	1,493
Separate account liabilities	123,586	118,385
Estimated Fair Value | Level 3
Assets
Mortgage loans	69,218	65,742
Policy loans	11,092	10,921
Real estate joint ventures	11	26
Other limited partnership interests	243	371
Other invested assets	394	352
Premiums, reinsurance and other receivables	3,089	3,127
Other assets	113	71
Liabilities
Policyholder account balances	116,637	110,359
Long-term debt	0	0
Collateral financing arrangements	945	978
Junior subordinated debt securities	0	0
Other liabilities	2,293	275
Separate account liabilities	$ 0	$ 0