Investment income and net realized and unrealized gains - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Unrealized investment losses on equity securities	$ 2,300
Realized losses from sales of securities investments	(600)	$ (2,500)
Realized gains on equity investment	1,200
Gain realized from termination fee paid by FNF	50,000	50,000
Net unrealized gains on equity securities		4,000
Impairment expenses		14,700
Realized gains from sales of equity investments with no previously readily determinable fair value			$ 1,300
Net unrealized investment losses recognized on equity securities still held	$ 2,311	$ (4,042)	$ 2,162