Income Taxes - Provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
U.S. federal	$ 24,880	$ 63,359	$ 49,985
U.S. state and local	6,038	15,130	19,290
Foreign	2,811	464	1,239
UBT	2,845	1,335	3,586
Total	36,574	80,288	74,100
Deferred:
U.S. federal	3,249	(25,103)	(9,972)
U.S. state and local	(1,912)	(4,025)	24,092
Foreign	(120)	(15)	0
UBT	(798)	1,291	2,267
Deferred tax (benefit) provision	419	(27,852)	16,387
Provision for income taxes	$ 36,993	$ 52,436	$ 90,487