Business Dispositions and Discontinued Operations - Major Classes of Assets and Liabilities Transferred by the Company to the Buyer in Connection with Sale (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Dec. 03, 2017
Assets
Assets	$ 156,551	$ 164,936
Liabilities
Liabilities	154,194	162,442
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business
Assets
Cash and investments	29,227	30,135
Reinsurance recoverables	20,701	20,785
Loss accrual	(3,195)	(3,257)
Other assets	1,425	1,439
Separate account assets	108,393	115,834
Assets	156,551	164,936
Liabilities
Reserve for future policy benefits and unpaid loss and loss adjustment expenses	14,282	14,482
Other policyholder funds and benefits payable	28,921	29,228
Long-term debt	142	142	$ 142
Other liabilities	2,456	2,756
Separate account liabilities	108,393	115,834
Liabilities	$ 154,194	$ 162,442