Related party transactions - Management and Incentive Fees (Details) - USD ($)				3 Months Ended		9 Months Ended
	Nov. 19, 2019	Nov. 18, 2019	Nov. 26, 2013	Sep. 30, 2020	Sep. 29, 2019	Sep. 30, 2020	Sep. 29, 2019	Dec. 31, 2019
Related Party Transaction
Number of stock options (in shares)				6,068,000		6,068,000		6,068,000
Payment of dividends						$ 0	$ 68,886,000
Due from (to) related party				$ 0		0		$ (6,500,000)
FIG LLC | New Media
Related Party Transaction
Annual management fee (percent)			1.50%
Incentive fee (percent)	17.50%	25.00%
Reduction in number of options issuable (percent)	50.00%
Reimbursement for expenses				591,000	$ 774,000	1,916,000	2,000,000
FIG LLC | New Media | Management Fee
Related Party Transaction
Incentive fee expense				4,269,000	2,456,000	12,702,000	7,368,000
Fees paid				8,943,000	2,456,000	16,326,000	8,623,000
FIG LLC | New Media | Incentive Fee
Related Party Transaction
Incentive fee expense				0	0	0	1,455,000
Fees paid				$ 0	1,455,000	$ 2,602,000	6,675,000
Manager | FIG LLC | New Media
Related Party Transaction
Shares issued to management (in shares)	4,205,607
Option | Manager | FIG LLC | New Media
Related Party Transaction
Stock options granted (in shares)	3,163,264
Stock price (in dollars per share)	$ 15.50
Consecutive trading days with certain price triggering vesting	20 days
Price of stock triggering option vesting (in dollars per share)	$ 20
Fortress Investment Group LLC
Related Party Transaction
Affiliates ownership						3.00%
Outstanding warrants						40.00%
Number of stock options (in shares)				6,068,075		6,068,075
Payment of dividends				$ 0	$ 200,000	$ 0	$ 700,000