Share Repurchase Plan (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule of Share Repurchases Under Share Repurchase Plan

Repurchases under this program to date have been as follows:

	2017		2016		2015		To Date
	(In millions, except per share amounts)
Total cost of shares repurchased	$	120	$	—	$	91	$	5,471
Total number of shares repurchased		2.63		—		1.45		66.74
Average cost per share (including transaction fees)	$	45.67	$	—	$	62.76	$	81.96