Related party transactions - Related party transactions with affiliated company - Additional Information 1 (Details) - Related Party With Investment Companies - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Related Party Transaction
Line of credit facility maximum borrowing capacity	$ 255,000,000		$ 275,000,000
Administrative Fees	1,200,000	$ 1,600,000
Waived Fees	500,000	500,000
Net fees	$ 700,000	$ 1,100,000
Credit Facilities Terms	The aggregate sum of all outstanding balances under all credit facilities that may be made available by BPPR, from time to time, to those investment companies for which BPPR acts as investment advisor or co-investment advisor, shall never exceed the lesser of $200 million or 10% of BPPR’s capital.
Line of credit facility average amount oustanding	$ 0