Shareholders' Equity - Schedule of Shares Repurchase Plans (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Shares Purchased		16.8
Average Cost per Share (USD per share)		$ 86.37
Total Purchased		$ 1,450,000,000
2017 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase			$ 1,400,000,000.0
Shares Purchased		7.4
Average Cost per Share (USD per share)		$ 94.54
Total Purchased		$ 700,000,000
2016 Program
Equity, Class of Treasury Stock [Line Items]
Amount of common stock authorized for repurchase				$ 1,400,000,000.0
Shares Purchased		9.4
Average Cost per Share (USD per share)		$ 79.93
Total Purchased		$ 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