Summary of Significant Accounting Policies - Fair Value Disclosures (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 318.1	$ 308.3	$ 288.3
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.5	6.9
U.S. and Non-U.S. Equities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at NAV	112.2	92.4
U.S. and Non-U.S. Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at NAV	181.1	185.8
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets measured at NAV	$ 23.3	$ 23.2