Cash and Investments - Short-term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 84	$ 84
Estimated Fair Value	84	84
Bond Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	84	84
Estimated Fair Value	$ 84	$ 84