Stock Based Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 25,850,000	$ 21,229,000	$ 15,500,000
Tax benefit related to share-based compensation expense	9,200,000	7,800,000	5,800,000
Unrecognized compensation cost related to non-vested share-based compensation arrangements	54,500,000
Unrecognized compensation cost, weighted average recognition period	2 years 8 months 1 day
Weighted average fair value of options granted	$ 12.53	$ 12.32	$ 8.02
Number of options that had exercise prices lower than the market price of common stock	2,700,000
Market price of common stock	$ 55.28
Total intrinsic value of options exercised	19,800,000	31,200,000	4,400,000
Weighted average fair value of restricted stock units and non-vested shares granted	$ 42.59
Cash received from stock option exercises and the issuance of stock under the Purchase Plan	30,300,000
Tax benefit realized for tax deductions from option exercises	6,800,000
Treasury stock, shares	54,071,000	54,018,000
Restricted stock units and non-vested shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of restricted stock units and non-vested shares granted	$ 42.27	$ 37.80	$ 24.38
Total intrinsic value of restricted stock units and non-vested shares vested	$ 26,700,000	$ 15,500,000	$ 9,700,000
2003 Employment Inducement Award Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock for grant under stock plan	2,250,000
2012 Long-Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock for grant under stock plan	6,000,000
Shares available for grants under stock plan	1,731,492
Stock option awards vesting period	4 years
2012 Long-Term Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards term	7 years
2012 Long-Term Incentive Plan | Awards Granted Prior to October 1, 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards vesting period	4 years
2012 Long-Term Incentive Plan | Awards Granted Prior to October 1, 2005 | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards term	10 years
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares of common stock for grant under stock plan	5,062,500
Shares available for grants under stock plan	2,707,966
Employee stock purchase plans, percentage of salary withheld through payroll deductions to purchase FICO common stock	10.00%
Employee stock purchase plans, purchase price of the stock as a percentage of fair market value on the exercise date	85.00%
Employee stock purchase plans, offering period (in months)	6 months