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	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	May 31, 2018	Dec. 31, 2017
Assets
Assets	$ 0		$ 0			$ 164,936
Liabilities
Liabilities	0		0			162,442
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, before Income Tax	$ (9)	$ 143	$ 113	$ 227
Assets
Cash and investments					$ 27,058	30,135
Reinsurance recoverables					20,718	20,785
Loss accrual					(3,044)	(3,257)
Other assets					2,907	1,439
Separate account assets					110,773	115,834
Assets					158,412	164,936
Liabilities
Reserve for future policy benefits and unpaid loss and loss adjustment expenses					14,308	14,482
Other policyholder funds and benefits payable					28,680	29,228
Long-term debt					142	142
Other liabilities					2,222	2,756
Separate account liabilities					110,773	115,834
Liabilities					$ 156,125	$ 162,442