Commitment and Contingencies, Other Than Loan Commitments - Scheduled Capital Account Withdrawal Requests (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Partners Capital Account Withdrawals [Abstract]
2018	$ 24,247
2019	14,994
2020	8,156
2021	4,779
2022	1,890
Thereafter	68
Total	$ 54,134