Fair Value of Financial Instruments - Fair Value Option (Details) - Merchant banking and other equity investments - Level III - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Fair Value, Option, Quantitative Disclosures [Line Items] | |||
Investments at fair value | $ 3.0 | $ 14.1 | |
Gains from changes in fair value | $ 0.6 | $ 1.6 | $ 1.8 |