Stockholders' Equity - Stock Compensation - Options - Net Tax Benefits (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Compensation
Provision (benefit) for income taxes	$ (11,635)	$ (2,330)	$ (36,328)	$ 5,762	$ 5,854	$ 782	$ 5,735	$ (3,209)	$ (44,531)	$ 9,162	$ 11,457
Stock Options
Stock Compensation
Provision (benefit) for income taxes									2,300	1,500	$ (5,100)
Excess tax benefits of tax deductions in recognized stock compensation expenses									2,700	1,800
Deficiency of tax deductions in recognized stock compensation expenses									$ 400	$ 300