Shares Used in Computing Net Income Per Share - Schedule of Weighted-Average Number of Shares (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Weighted-average common shares outstanding used for the calculation of net income per share – basic	211.8	222.0	213.2	222.8
Common stock equivalents (in shares)	4.5	3.6	4.6	3.7
Weighted-average common shares outstanding used for the calculation of net income per share – diluted	216.3	225.6	217.8	226.5