Equity (Tables)
 3 Months Ended
Mar. 31, 2018
Equity [Abstract]  
Share Repurchases
Total share repurchases were as follows:
 
Three Months Ended 
 March 31,
(In millions, except per share data)
2018
 
2017
Number of shares repurchased
19

 
9

Cash paid for shares repurchased
$
1,327

 
$
420

Average cost per share
$
68.74

 
$
50.15