Financial Instruments (Narrative) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financial Instruments [Line Items]
Realized loss or gains	$ 0	$ 0	$ 0
US treasury and government short-term debt securities
Financial Instruments [Line Items]
Available for sale securities maturity period		1 year