Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - Valuation allowance for deferred tax asset - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement in Valuation Allowances and Reserves
Balance at beginning of year	$ 110,781	$ 142,496	$ 178,156
Additions charged to expense	23,150	5,324	3,682
Deductions	(17,388)	(37,039)	(39,342)
Balance at end of year	$ 116,543	$ 110,781	$ 142,496