Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 1.2	$ 2.5
Contingent consideration associated with CDI acquisition	0.3	0.3
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	1.2	2.5
Contingent consideration associated with CDI acquisition	0.0	0.0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities
Contingent consideration associated with CDI acquisition	0.0	0.0
Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	0.0	0.0
Contingent consideration associated with CDI acquisition	$ 0.3	$ 0.3