Stock Plans - Additional Information (Detail) (USD $)	12 Months Ended									0 Months Ended	1 Months Ended	12 Months Ended				12 Months Ended		0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2014 Restricted stock	Sep. 30, 2013 Restricted stock	Sep. 30, 2012 Restricted stock	Sep. 30, 2014 Performance Based	Sep. 30, 2013 Performance Based	Sep. 30, 2012 Performance Based	Feb. 08, 2012 Employee Stock Purchase Plan, 1995 Plan	Feb. 29, 1996 Employee Stock Purchase Plan, 1995 Plan	Sep. 30, 2014 Employee Stock Purchase Plan, 1995 Plan	Feb. 12, 1996 Employee Stock Purchase Plan, 1995 Plan Before Amendment	Feb. 08, 2012 Employee Stock Purchase Plan, 1995 Plan After Amendment Maximum	Sep. 30, 2014 Equity Incentive Plan 2000	Sep. 30, 2014 Equity Incentive Plan 2000 Restricted stock	Sep. 30, 2014 Equity Incentive Plan 2000 Restricted stock Share Vesting Over Three Year Period	Oct. 26, 2005 Helix Stock Options	Sep. 30, 2014 Helix Stock Options
Equity Incentive Plan [Line Items]
Vesting period				3 years												3 years
Shares of common stock reserved for issuance															9,000,000
Options outstanding	5,550	15,540													0			689,622	5,550
Shares available for grant	2,486,983														2,486,983				0
Options to purchase Helix common stock																		765,480
Closing stock price	$ 10.51
Total intrinsic value of options exercised	$ 0	$ 19,000	$ 56,000
Cash received from employee stock option exercises	0	67,000	103,000
Awards granted (USD per share)				$ 9.49	$ 9.33	$ 11.80
Fair value of restricted stock awards vested				5,600,000	7,300,000	5,600,000
Unrecognized compensation cost				$ 17,200,000
Unrecognized compensation cost, estimated weighted average amortization period				1 year 8 months 12 days
Equity incentive plan vesting in year one, percentage																33.33%
Equity incentive plan vesting in year two, percentage																33.33%	50.00%
Equity incentive plan vesting in year three, percentage																33.34%	50.00%
Employee stock purchase plan, offering period											6 months
Maximum award over targeted number of awards							200.00%
Shares that could vest under terms of award							1,297,546	460,615	0
Number of shares over the target grant							458,796	(216,760)
Shares of common stock available for purchase												649,355	3,000,000	4,000,000
Employee stock purchase plan, price per share percentage											85.00%
Additional shares of common stock available for purchase										1,000,000
Maximum percentage of base pay withheld and applied toward the purchase of shares										10.00%
Stock purchase under employee stock purchase plan												3,350,645