Stock Plans (Activity for Performance Share Units) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Performance Shares [Member]
Number of Shares (in shares):
Beginning Balance (in shares)		427,570
Granted (in shares)		393,460
Vested (in shares)		0
Forfeited (in shares)		0
Ending Balance (in shares)		821,030	427,570
Weighted-Average Grant Date Fair Value:
Compensation expense for share-based awards		$ 37	$ 27
Performance Share Units, TSR Relative To Customer Peer Group [Member]
Weighted-Average Grant Date Fair Value:
Beginning Balance (in dollars per share)		$ 104.60
Granted (in dollars per share)	[1]	128.72	$ 104.60
Vested (in dollars per share)		0.00
Forfeited (in dollars per share)		0.00
Ending Balance (in dollars per share)		$ 116.16	$ 104.60
Weighted-average grant date fair value	[1]	$ 25	$ 22
Performance Share Units, Other Performance Factors [Member]
Weighted-Average Grant Date Fair Value:
Beginning Balance (in dollars per share)		$ 89.02
Granted (in dollars per share)	[2]	98.29	$ 89.02
Vested (in dollars per share)		0.00
Forfeited (in dollars per share)		0.00
Ending Balance (in dollars per share)		$ 93.46	$ 89.02
Weighted-average grant date fair value	[2]	$ 19	$ 19

[1] The grant date fair value of the PSU market based awards subject to the TSR performance factor was determined by using the Monte Carlo simulation model.

[2] The grant date fair value of the PSU awards subject to the other performance factors was determined by using the average of the high and low market price of PMI’s stock at the date of grant.