Business, Basis of Presentation and Summary of Significant Accounting Policies (Other Revenues) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Other revenues	$ 475	$ 292	$ 949	$ 634
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Other revenues	328		650
Corporate and Other | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Fee based investment management service revenue	74		145
U.S. | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Prepaid legal plans and administrative-only contracts	126		255
MetLife Holdings | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Distribution and Administrative Services fees	$ 56		$ 114