Shareholders' Equity - Schedule of Shares Repurchase Plans (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Shares Purchased	3.7		13.1
Average Cost per Share (USD per share)	$ 93.39		$ 83.77
Total Purchased	$ 350,000,000		$ 1,100,000,000
2017 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase				$ 1,400,000,000.0
Shares Purchased	3.7		3.7
Average Cost per Share (USD per share)	$ 93.39		$ 93.39
Total Purchased	$ 350,000,000		$ 350,000,000
2016 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase					$ 1,400,000,000.0
Shares Purchased	0.0		9.4
Average Cost per Share (USD per share)	$ 0.00		$ 79.93
Total Purchased	$ 0		$ 750,000,000
Boston Financial Data Services, Inc. and International Financial Data Services
Equity, Class of Treasury Stock [Line Items]
Common stock received in acquisition		$ 158,000,000