Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares
Number of Shares
Outstanding beginning balance (in shares) | shares	5.0
Granted (in shares) | shares	0.0
Exercised (in shares) | shares	(1.2)
Forfeited or expired (in shares) | shares	(0.1)
Outstanding ending balance (in shares) | shares	3.7
Exercisable (in shares) | shares	2.9
Weighted Average Exercise Price per Share
Outstanding beginning balance (in dollars per share) | $ / shares	$ 30.08
Granted (in dollars per share) | $ / shares	0.00
Exercised (in dollars per share) | $ / shares	29.49
Forfeited or expired (in dollars per share) | $ / shares	31.60
Outstanding ending balance (in dollars per share) | $ / shares	30.23
Exercisable (in dollars per share) | $ / shares	$ 29.88
Weighted Average Remaining Contractual Term (years), Outstanding	2 years 6 months
Weighted Average Remaining Contractual Term (years), Exercisable	2 years 2 months 12 days
Aggregate Intrinsic Value, Exercised | $	$ 22.6
Aggregate Intrinsic Value, Outstanding | $	73.7
Aggregate Intrinsic Value, Exercisable | $	$ 61.5