Employee Benefits - Summary of Stock Option Plans (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding beginning of period, Options | shares	990
Grants, Options | shares	367
Exercises, Options | shares	(203)
Forfeitures, Options | shares	(2)
Cancellations, Options | shares	(49)
Outstanding end of period, Options | shares	1,103
Exercisable end of period, Options | shares	674
Outstanding beginning of period, Weighted Average Exercise Price | $ / shares	$ 17.36
Grants, Weighted Average Exercise Price | $ / shares	10.07
Exercises, Weighted average exercise price | $ / shares	17.83
Forfeitures, Weighted average exercise price | $ / shares	14.74
Cancellations, Weighted average exercise price | $ / shares	21.62
Outstanding end of period, Weighted Average Exercise Price | $ / shares	14.67
Exercisable end of period, Weighted average exercise price | $ / shares	$ 16.86
Outstanding end of period, Weighted Average remaining life	6 years 10 months 20 days
Exercisable end of period, Weighted Average remaining life	5 years 9 months 18 days
Outstanding end of period, Aggregate intrinsic value | $	$ 3,483
Exercisable end of period, Aggregate intrinsic value | $	$ 984