Fair Value Measurements - Summary of Assets Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 2,600	$ 4,800
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	2,557	4,849
Nonrecurring basis | Quoted Prices in Active Markets for Identical Assets Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	0	0
Nonrecurring basis | Significant Other Observable Inputs Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	0	0
Nonrecurring basis | Significant Unobservable Inputs Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loan participations held-for-investment	$ 2,557	$ 4,849