Common Share Repurchases (details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Common Share Repurchases disclosure
Number of shares repurchased (in shares) | shares	5.1
Cost of shares repurchased	$ 550
Average cost per share repurchased | $ / shares	$ 108.46
Remaining capacity under share repurchase authorization	$ 2,780
Number of shares acquired to cover tax withholding costs and exercise costs (in shares) | shares	0.5
Cost of shares acquired to cover tax withholding costs and exercise costs	$ 59