Employee Incentive, Retirement, Deferred Compensation, and Career Achievement Plans (Schedule of Components and Amounts Impacting AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income
Beginning balance	$ 1	$ 0
Actuarial gain/(loss)	(11)	1
Ending balance	(10)	1
Net gain/(loss)			$ (10)	$ 1
Amount recognized in AOCI	$ 1	$ 0	(10)	1
Tax effect			4	0
Net amount recognized in AOCI			$ (6)	$ 1