Income Taxes (Reconciliation of Provision for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Provision for Income Taxes
Federal income tax (benefit) expense at statutory tax rate	$ (89,425)	$ 27,849	$ 53,892
State income taxes, net of federal tax benefit	(18,442)	9,011	7,753
Stock based compensation	1,706
Impact of federal tax law change		211	(53,348)
Officers' compensation	2,938	3,078	2,622
Goodwill impairment	43,990
Domestic production activities deduction			(2,668)
Noncontrolling interest	(6,064)	(3,232)	(2,137)
Federal R&D credits	(3,998)	(2,658)	(470)
Reversal of reserve for uncertain tax positions and taxes payable due to statue expirations	(773)	(1,958)	(4,337)
Foreign tax differences	4,940	(19)	(389)
Other	(481)	2,550	(1,487)
Total tax (benefit) expense	$ (65,609)	$ 34,832	$ (569)
Reconciliation of Effective Income Tax Rate
Federal income tax expense at statutory tax rate (Rate)	21.00%	21.00%	35.00%
State income taxes, net of federal tax benefit (Rate)	4.30%	6.80%	5.00%
Stock based compensation (Rate)	(0.40%)
Impact of federal tax law change (Rate)		0.20%	(34.60%)
Officers' compensation (Rate)	(0.70%)	2.30%	1.70%
Goodwill impairment (Rate)	(10.30%)
Domestic production activities deduction (Rate)			(1.70%)
Noncontrolling interest (Rate)	1.40%	(2.40%)	(1.40%)
Federal R&D credits (Rate)	0.90%	(2.00%)	(0.40%)
Reversal of taxes payable due to statue expiration (Rate)	0.20%	(1.50%)	(2.80%)
Foreign tax differences (Rate)	(1.20%)		(0.30%)
Other (Rate)	0.20%	1.90%	(0.90%)
Total (benefit) provision (Rate)	15.40%	26.30%	(0.40%)