Stock-Based Compensation - Schedule of Other Stock Option Statistics (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Other disclosures
Total unrecognized compensation cost on nonvested options	$ 4.6
Non-qualified stock options
Other disclosures
Aggregate intrinsic value of outstanding options	57.2	$ 51.7
Aggregate intrinsic value of exercisable options	53.2	48.7
Total intrinsic value of options exercised	$ 6.7	$ 26.0
Total number of options exercisable (in shares)	1.8	1.8
Weighted average exercise price of options exercisable (in dollars per share)	$ 21.99	$ 19.83
Total unrecognized compensation cost on nonvested options	$ 1.1	$ 1.2