Contribution Transaction Contribution Transaction (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ (2)	$ (365)
Other Comprehensive Income (Loss), Net of Tax	$ (823)	148
Scenario, Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)		(129)
Other Comprehensive Income (Loss), Net of Tax		$ (143)