Fair Value of Financial Instruments - Investments at Fair Value Using Net Asset Value Per Share As Practical Expedient (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Limited liability investments, at fair value	$ 30,986	$ 29,078
Measured at Net Asset Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Limited liability investments, at fair value	$ 26,573	$ 24,686