Income Taxes from Continuing Operations - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed “expected” tax provision	$ (20,719)	$ 94,955	$ 81,255
Change in income taxes resulting from:
State income taxes, net of Federal income tax	(537)	4,501	5,520
Change in state income tax rate, net of Federal income tax	(4,714)	0	0
Foreign income tax provision (benefit)	2,206	1,580	(1,130)
Deduction for domestic production activities	(2,527)	(7,280)	(6,882)
Stock compensation	(1,316)	(11,395)	0
R&D tax credits	(1,200)	(825)	(677)
Nondeductible acquisition fees	1,974	39	165
Interest and penalties from Federal audit	15,650	0	0
Federal rate change	(26,902)	0	0
Discrete adjustments to prior year	1,561	0	0
Other expense, net	1,201	2,564	682
Valuation allowance change	675	2,918	2,425
Income tax provision	$ (34,648)	$ 87,057	$ 81,358