Income Taxes (Schedule Of Differences Between The Income Tax Expense (Benefit)Computed At The Statutory Federal income Tax Rate And As Presented On The Consolidated Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019	[1],[2]	Sep. 30, 2019	[1],[2]	Jun. 30, 2019	[1],[2]	Mar. 31, 2019	[1],[2]	Dec. 31, 2018	[2]	Sep. 30, 2018	[2]	Jun. 30, 2018	[2]	Mar. 31, 2018	[2]	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Tax expense at federal statutory rate																	$ (36,317)	$ 1,060	$ (19,400)
State income tax expense, net of federal benefit																	(7,839)	702	(1,159)
Nondeductible compensation																	762	921	222
Noncontrolling interests																	(3,961)	(4,370)	(7,199)
Unrecognized tax benefit																	36	15,148	25,720
R&D Credits																	(323)	(34,979)	(74,033)
Increase in valuation allowance																	25,314
Disposition of subsidiary																	(373)	(1,022)
Tax Cuts and Jobs Act impact																		278	(57,223)
Stock compensation																	369	993
Audit adjustments																		559
Amended return adjustments																		374
Other																	1,016	189	1,011
Income tax expense (benefit)	$ 19,514		$ (12,565)		$ (15,322)		$ (12,943)		$ 14,457		$ (14,941)		$ (12,498)		$ (7,165)		$ (21,316)	$ (20,147)	$ (132,061)

[1] The fourth quarter of 2019 includes the recognition of a $25.3 million valuation allowance which impacted income tax expense.

[2] GPCC results prior to its disposition are classified as discontinued operations in current and prior period consolidated financial statements.