Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2015 USD ($)	Sep. 30, 2015 USD ($) Customer $ / shares shares	Sep. 30, 2014 USD ($) Customer	Mar. 31, 2015 USD ($) Customer	Jun. 30, 2014 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of shares repurchased | shares		299,620		559,702
Treasury Stock, Value, Acquired, Cost Method		$ 9,700,000		$ 18,800,000
Average price | $ / shares		$ 32.37		$ 33.55
Maturities of short term investment interest-bearing securities				90 days
Investment in private equity				$ 600,000	$ 800,000
Accounts receivable due period				30 days
Private Equity Funds [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Investments approved by board of directors							$ 2,000,000
Investment in private equity			$ 600,000			$ 1,400,000
Impairment on investment				$ 0		$ 0
Minimum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment				1 year
Maximum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment				7 years
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Maximum customer risk percentage				10.00%	10.00%
Number of customer | Customer				0	0
Credit Concentration Risk [Member] | Accounts Receivable [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Maximum customer risk percentage				10.00%		10.00%
Number of customer | Customer				0		0
Fair Value, Inputs, Level 2 [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Transfer of assets		$ 0		$ 0
Fair Value, Inputs, Level 3 [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Transfer of assets		$ 0		$ 0
Computer Software Property and Equipment [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment				5 years
Subsequent Event [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of shares repurchased | shares	99,403
Treasury Stock, Value, Acquired, Cost Method	$ 3,287,000
Average price | $ / shares	$ 33.07