Dispositions - Separation of Brighthouse - Ongoing Reinsurance Transactions (Effects of Reinsurance on Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Premiums and Other Receivables, Net	$ 18,423	$ 15,445
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	18,419	17,590	$ 17,430
Total assets	36,842	33,035
Liabilities
Future policy benefits	177,974	166,636
Policyholder account balances	182,518	172,486	$ 165,130
Other policy-related balances	15,515	13,402
Other Liabilities	23,982	23,735
Total liabilities	399,989	376,259
Direct
Assets
Premiums and Other Receivables, Net	6,300	5,927
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	18,350	17,878
Total assets	24,650	23,805
Liabilities
Future policy benefits	174,694	165,121
Policyholder account balances	182,226	171,961
Other policy-related balances	14,962	13,071
Other Liabilities	17,077	18,815
Total liabilities	388,959	368,968
Assumed
Assets
Premiums and Other Receivables, Net	866	543
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	398	16
Total assets	1,264	559
Liabilities
Future policy benefits	3,280	1,515
Policyholder account balances	293	527
Other policy-related balances	520	324
Other Liabilities	1,896	405
Total liabilities	5,989	2,771
Ceded
Assets
Premiums and Other Receivables, Net	11,257	8,975
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	(329)	(304)
Total assets	10,928	8,671
Liabilities
Future policy benefits	0	0
Policyholder account balances	(1)	(2)
Other policy-related balances	33	7
Other Liabilities	5,009	4,515
Total liabilities	5,041	$ 4,520
Affiliated Entity [Member] | Assumed
Assets
Premiums and Other Receivables, Net	167
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	384
Total assets	551
Liabilities
Future policy benefits	1,734
Other policy-related balances	119
Other Liabilities	1,458
Total liabilities	3,311
Affiliated Entity [Member] | Ceded
Assets
Premiums and Other Receivables, Net	1,793
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	(40)
Total assets	1,753
Liabilities
Future policy benefits	0
Other policy-related balances	28
Other Liabilities	19
Total liabilities	$ 47