Fair Value Measurements - Financial Assets and Liabilities Accounted at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Registered investment companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Registered investment companies	[1]	$ 3.6	$ 3.4

[1] Registered investment companies are classified as available-for-sale securities and are valued using quoted prices in active markets multiplied by the number of shares owned.