Indebtedness (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended			3 Months Ended	4 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended		3 Months Ended		3 Months Ended		6 Months Ended	3 Months Ended	9 Months Ended			0 Months Ended
	Apr. 18, 2012 Y	Mar. 31, 2012	May 31, 2008	May 07, 2008	Mar. 31, 2012 2008 Term Loan [Member]	May 07, 2008 2008 Term Loan [Member] Y	Mar. 31, 2012 Line Of Credit [Member]	Sep. 28, 2007 Line Of Credit [Member] Y	Mar. 31, 2012 Line Of Credit [Member] 2012 Facility [Member]	Apr. 18, 2012 Line Of Credit [Member] 2012 Facility [Member]	Mar. 31, 2012 Commercial Paper [Member]	Oct. 03, 2007 Commercial Paper [Member]	Mar. 31, 2012 2010 Senior Notes [Member]	Mar. 31, 2012 Series 2007-1 Notes [Member]	Jul. 09, 2007 Series 2007-1 Notes [Member] Y	Mar. 31, 2012 Series 2005-1 Notes [Member]	Sep. 30, 2005 Series 2005-1 Notes [Member] Y	Dec. 31, 2010 Series 2005-1 Notes [Member]	Mar. 31, 2012 Senior Notes 7.61 Percent Due September 30th 2005 [Member]	Nov. 04, 2011 Copal [Member]
Debt Instrument [Line Items]
Date the credit facility was entered							2007-09-28		2012-04-18
Date of expiry of credit facility							2012-09-28		2017-04-17
Financial covenants to be maintained at the end of any fiscal quarter							Debt/EBITDA ratio of not more than 4.0 to 1.0
Five-year senior, unsecured revolving credit facility								$ 1,000,000,000		$ 1,000,000,000		$ 1,000,000,000
Non-interest bearing note issued																				14,200,000
Notes due description																				(i) the fourth anniversary date of the note or (ii) within a time frame set forth in the acquisition agreement relating to the resolution of certain income tax uncertainties pertaining to the transaction.
Notes repayment description																				(i) two business days subsequent to the exercise of the put/call option to acquire the remaining shares of Copal or (ii) the tenth anniversary date of the issuance of the note.
Maturity date of CP Notes (in days)											397 days
Interest on borrowings under the Term Loan						LIBOR plus a margin that can range from 125 basis points to 175 basis points	LIBOR plus a premium that could range from 16.0 to 40.0 basis points		LIBOR plus a premium that can range from 77.5 basis points to 120 basis points
Utilization fee							5.0 basis points on borrowings outstanding when the aggregate amount outstanding exceeded 50% of the total facility
Quarterly facility fees							4.0 to 10.0 basis points per annum		10 basis points of the facility amount to 17.5 basis points
Debt to EBITDA ratio not to exceed at the end of any fiscal quarter					at the end of any fiscal quarter				Debt to EBITDA Ratio of not more than 4 to 1 at the end of any fiscal quarter					Debt/EBITDA ratio to exceed 4.0 to 1.0 at the end of any fiscal quarter
Debt/EBITDA ratio					4.0									4.0
Date of agreement with the lenders for the five year senior unsecured term loan					May 7, 2008								2010-08-19	September 7, 2007		2005-09-30
Entered with several lenders into a five year senior unsecured term loan/Refinance of Senior Notes						150,000,000							500,000,000	300,000,000		300,000,000			300,000,000
Minimum amount for default on senior notes payable		50,000,000
Minimum percentage for default on senior notes payable		Upon the occurrence and during the continuation of an event of default under the Indenture, the notes may become immediately due and payable either automatically or by the vote of the holders of more than 25% of the aggregate principal amount of all of the notes then outstanding
Minimum percentage of aggregate principal amount of all notes		25.00%
Senior Unsecured Notes, interest													5.50%	6.06%		4.98%			7.61%
Maturity date of Senior Unsecured Notes													Sep. 01, 2020	Sep. 07, 2017		Sep. 30, 2015
Prepayment and purchase feature of Senior Unsecured Notes		In the event that Moody's pays all, or part, of the Series 2005-1 Notes in advance of their maturity, such prepayment will be subject to a Make Whole Amount.											The Company may prepay the 2010 Senior Notes, in whole or in part, at any time at a price equal to 100% of the principal amount being prepaid, plus accrued and unpaid interest and a Make-Whole Amount. Additionally, at the option of the holders of the notes, the Company may be required to purchase all or a portion of the notes upon occurrence of a "Change of Control Triggering Event," as defined in the Indenture, at a price equal to 101% of the principal amount thereof, plus accrued and unpaid interest to the date of purchase	The Company may prepay the Series 2007-1 Notes, in whole or in part, at any time at a price equal to 100% of the principal amount being prepaid, plus accrued and unpaid interest and a Make Whole Amount
Percentage of principal amount being prepaid, plus accrued and unpaid interest													100.00%
Percentage of principal amount, plus accrued and unpaid interest to the date of purchase													101.00%
Issuance of additional principal amount of Senior Notes within five years from time to time														500,000,000
Interest rate swaps total notional amount			$ 150,000,000	$ 150,000,000														$ 300,000,000
Debt instrument term (in years)	5					5		5	5						10		10