Income Taxes - Differences Between Income Tax Provision (Benefit) and Income Taxes Computed using Applicable U.S. Statutory Federal Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Income tax provision (benefit) computed at federal statutory rate		$ 2,217	$ 6,177	$ (217)
State income taxes, net of federal benefit		113	243	(12)
Foreign income taxed at different rates		(755)	(938)	(596)
Dividends		(1,666)	(1,069)	(1,373)
Change in deferred tax asset valuation allowance	$ 79,300	77,531	(36)	453
Reduction in uncertain tax positions		(1,543)	(1,207)	(1,236)
Nondeductible compensation		782	1,325	1,064
Tax credits generated		(1,786)	(1,741)	(704)
Travel and entertainment		274	314	220
Merger costs		503	228	187
Other		140	134	234
Income tax provision (benefit)		$ 75,810	$ 3,430	$ (1,980)