Stock Plans - Additional Information (Detail) (USD $)	12 Months Ended				12 Months Ended						1 Months Ended		12 Months Ended			12 Months Ended			12 Months Ended	1 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010	Sep. 28, 2012	Sep. 30, 2012 Stock options	Sep. 30, 2012 Restricted stock	Sep. 30, 2011 Restricted stock	Sep. 30, 2010 Restricted stock	Sep. 30, 2012 Restricted stock Maximum	Sep. 30, 2012 Restricted stock Senior Management	Feb. 29, 1996 Employee Stock Purchase Plan, 1995 Plan	Feb. 12, 1996 Employee Stock Purchase Plan, 1995 Plan	Sep. 30, 2012 Employee Stock Purchase Plan, 1995 Plan	Feb. 12, 1996 Employee Stock Purchase Plan, 1995 Plan Before Amendment	Feb. 12, 1996 Employee Stock Purchase Plan, 1995 Plan After Amendment Maximum	Sep. 30, 2012 1998 Employee Equity Incentive Plan	Sep. 30, 2012 1998 Employee Equity Incentive Plan Stock options	Sep. 30, 2012 1993 Non-Employee Director Stock Option Plan	Sep. 30, 2012 1993 Non-Employee Director Stock Option Plan Stock options	Oct. 31, 2005 Helix Stock Options	Sep. 30, 2012 Helix Stock Options	Sep. 30, 2012 Equity Incentive Plan 2000	Sep. 30, 2012 Equity Incentive Plan 2000 Restricted stock	Sep. 30, 2012 Equity Incentive Plan 2000 Restricted stock Senior Management	Sep. 30, 2012 Equity Incentive Plan 2000 Restricted stock Share Vesting Over Three Year Period
Equity Incentive Plan [Line Items]
Equity incentive plan, vesting period					4 years				4 years								4 years		5 years			4 years	3 years
Equity incentive plan, expiration Period																	7 years		10 years			7 years
Shares of common stock reserved for issuance																						9,000,000
Options outstanding	193,182	370,137														1,000		10,000		689,622	37,182	145,000
Shares available for grant	3,848,477																				456,343	3,392,134
Restricted stock or units issued net of cancellations																							685,171
Awards granted						1,887,419				1,527,000														1,054,250
Restricted stock or units vesting description																							These restricted stock awards generally have the following vesting schedules: immediate; three year vesting in which one-quarter vest at the end of Year 1, one-quarter vest at the end of Year 2 and one-half vest at the end of Year 3; and three year vesting in which one-third vest at the end of Year 1, one-third vest at the end of Year 2 and one-third vest at the end of Year 3.
Equity incentive plan vesting in year one, percentage																							33.33%		25.00%
Equity incentive plan vesting in year two, percentage																							33.33%		25.00%
Equity incentive plan vesting in year three, percentage																							33.33%		50.00%
Options forfeited due to employee terminations																3,211,820
Options to purchase Helix common stock																				765,480
Closing stock price				$ 8.04
Total intrinsic value of options exercised	$ 56,000	$ 15,000	$ 3,000
Cash received from employee stock option exercises	103,000	6,000	19,000
Weighted average grant date fair value, Awards granted						$ 11.80	$ 11.27	$ 8.73
Fair value of restricted stock awards vested						5,600,000	7,400,000	6,800,000
Unrecognized compensation cost						$ 8,800,000
Unrecognized compensation cost, estimated weighted average amortization period						1 year 9 months 18 days
Employee stock purchase plan, description											Under the 1995 Plan, eligible employees may purchase up to an aggregate of 3,000,000 shares during six-month offering periods commencing on February 1 and August 1 of each year at a price per share of 85% of the lower of the fair market value price per share on the first or last day of each six-month offering period. On February 8, 2012, the stockholders approved an amendment to the 1995 Plan to increase the number of shares of the Company’s common stock available for issuance by 1,000,000 shares, from 3,000,000 to 4,000,000 shares. Participating employees may elect to have up to 10% of their base pay withheld and applied toward the purchase of such shares.
Additional shares of common stock available for purchase												1,000,000
Shares of common stock available for purchase													1,090,355	3,000,000	4,000,000
Employee stock purchase plan, offering period											6 months
Employee stock purchase plan, price per share percentage											85.00%
Maximum percentage of base pay withheld and applied toward the purchase of shares											10.00%
Shares of common stock purchased under the 1995 Plan													2,909,645