Accrued Liabilities (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accrued liabilities	$ 14,498	$ 14,498		$ 11,923
Severance Costs	3,600	6,600
Severance paid	0	600
Forecast [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Severance Costs			$ 13,000
Discontinued Operations, Held-for-sale [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accrued liabilities	$ 15,196	$ 15,196		$ 16,400