Net investment income - TP Fund Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Total investments in securities	$ 1,059,231	$ 989,701
Cash and cash equivalents	513,783	639,415
Due from brokers	81,142	0
Interest and dividends receivable	1,835	2,178
Other assets	20,171	20,555
Total assets	3,534,462	3,439,694
Liabilities
Accounts payable and accrued expenses	13,963	17,816
Securities sold, not yet purchased, at fair value	15,389	0
Interest and Dividends Payable	1,110	3,055
Total liabilities	2,105,892	2,025,620
TP Fund
Assets
Total investments in securities	1,865,701	1,620,531
Cash and cash equivalents	40,069	52
Due from brokers	175,067	162,682
Derivative assets, at fair value	13,316	21,861
Interest and dividends receivable	4,398	1,210
Other assets	186	212
Total assets	2,098,737	1,806,548
Liabilities
Accounts payable and accrued expenses	1,731	2,417
Securities sold, not yet purchased, at fair value	250,537	283,711
Securities sold under agreement to repurchase	15,173	0
Due to brokers	770,225	426,612
Derivative liabilities, at fair value	31,260	19,282
Withdrawals payable to General Partner	0	42,381
Interest and Dividends Payable	913	972
Management Fee Payable	224	256
Total liabilities	1,070,063	775,631
Partners' Capital	$ 1,028,674	$ 1,030,917