Note 12 - Credit Facilities and Indebtedness (Detail) In Millions, except Per Share data, unless otherwise specified	0 Months Ended			12 Months Ended						12 Months Ended
	Jun. 08, 2010 USD ($)	Jun. 15, 2009 USD ($)	May 11, 2009 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2010 USD ($)	Sep. 30, 2010 HKD	Dec. 15, 2009 USD ($)	May 31, 2009 USD ($)	Sep. 30, 2012 Interest Coverage Ratio [Member]	Sep. 30, 2012 Net Funded Debt Leverage Ratio [Member]
Line Of Credit Facility Revolving Credit				$ 140.0
Line of Credit Facility, Remaining Borrowing Capacity				587.7
Line of Credit Facility Reserved for Letters of Credit				22.3
Potential Increase In Credit Facility				250.0
Line of Credit Facility, Interest Rate Description				Interest rates and facility fees are based on our public debt ratings or our Net Funded Debt to EBITDA ratio (debt minus unrestricted cash and investments in excess of $150.0 million), whichever is more favorable to IGT. At September 30, 2012 our interest rate was LIBOR plus 122.5 bps on borrowings with a facility fee of 27.5 bps.
Debt Instrument, Covenant Description										3.0	3.5
NotesAggregatePrincipalAmount			850.0
Proceeds from Issuance of Private Placement			822.5
Deferred Offering Costs	3.0	4.0	27.5
Debt Instrument, Convertible, Terms of Conversion Feature			Each $1,000 Note is initially convertible into 50.0808 shares of IGT Common Stock, representing a conversion price of $19.97 per share.
Debt Instrument, Convertible, Conversion Price (in Dollars per share)				$ 19.97			0.96		$ 19.97
Debt Instrument, Convertible, Carrying Amount of Equity Component									99.7
Debt Instrument, Interest Rate, Effective Percentage								6.20%	8.70%
Initial Note Conversion Price (in Dollars per share)			$ 30.14						$ 30.14
Share Price Increase Percentage			10.00%
Conversion of Stock, Shares Issued (in Shares)			3.9
Derivative, Cost of Hedge Net of Cash Received				177.3
Deferred Tax Assets, Hedging Transactions				65.5
Derivative, Cash Received on Hedge			66.8	66.8
CommonSharesCoveredByHedge (in Shares)			42.6	42.6
Derivative, Price Risk Option Strike Price (in Dollars per Item)				19.97
MaximumSharesDelivered (in Shares)			72.6
Aggregate Principal Amount	300.0	500.0						701.2
Proceeds from Issuance of Long-term Debt	295.7	493.3		280.0	95.0	1,420.8
Debt Instrument, Unamortized Discount	1.3	2.7			2.9			43.7
RemainingRedemption								$ 5.8