Stock-Based Compensation - Assumptions Used Estimate Fair Value of Employee Stock Purchase Plans (Detail) - $ / shares shares in Thousands	6 Months Ended				12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares purchased for offering period	5,360	4,668	4,184	1,536
Fair value per share	$ 1.90	$ 1.25	$ 1.75	$ 2.28
Assumptions
Risk-free interest rate (average)	0.05%	0.12%	0.29%	1.84%	0.87%	0.44%
Weighted average expected life (years)	6 months	6 months	6 months	6 months	6 years 2 months 12 days	6 years 2 months 12 days
Volatility (average)	44.60%	47.10%	86.80%	86.30%	74.50%	80.80%