Retirement and Deferred Compensation Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement [Abstract]
Net periodic benefit expense (recovery)	$ (3)	$ 5	$ (6)
Expected benefit payments in the next fiscal year	112
Defined contribution plans expense	88	86	82
Deferred compensation plans expense	35	33	$ 10
Elective Contribution [Member]
Statement [Abstract]
Pension contributions	$ 10	$ 4