Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Narrative (Details)

v3.19.1
Fair Value Measurements - Narrative (Details) - Compstak - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Aug. 31, 2016
Convertible Preferred Stock | Other Assets | Series A-1      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Carrying value of investment $ 5.6 $ 3.0 $ 3.0
Level 2 | Non recurring      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investment gain $ 2.6