Accrued Liabilities (Narrative) (Detail) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2020		Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accrued liabilities		$ 11,959	[1]		$ 11,923	[2]
Severance Costs		3,000
Accrued liabilities, amounts received in advance of revenue recognition		4			5
Severance paid		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	[1]	$ 17,122			$ 16,400

[1] unaudited

[2] Note 1