Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect on income from continuing operations due to ASU	$ 16.4	$ 16.4	$ 21.4	$ 19.2	$ 14.5	$ 13.5	$ 16.4	$ 16.1	$ 73.4	$ 60.5	$ 68.0
Effect on income tax provision, due to early of adoption of ASU									$ (29.6)	$ (29.4)	$ (7.5)
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect on income from continuing operations due to ASU	1.8	0.4	0.7	0.2
Effect on income tax provision, due to early of adoption of ASU	$ 1.8	$ 0.4	$ 0.7	$ 0.2