Commitments and Contingencies - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions | May. 21, 2015 | Sep. 19, 2014 | Jun. 30, 2015 | Jun. 30, 2015 | Jun. 30, 2014 | Jun. 30, 2015 | Jun. 30, 2014 | Dec. 31, 2014 | Nov. 20, 2014 | Sep. 18, 2014 | Sep. 17, 2014 | Feb. 06, 2014 | Feb. 04, 2014 | Dec. 31, 2013 | Dec. 13, 2012 |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Annual rent expense | | | | $ 6,700,000 | $ 6,800,000 | $ 13,500,000 | $ 13,400,000 | | | | | | | | |
Shares repurchases, value | | | $ 669,400,000 | 669,400,000 | | $ 669,400,000 | | | | | | | | | |
Common shares received | | | | | | 14.4 | | | | | | | | | |
Long-term debt | | | 800,000,000 | 800,000,000 | | $ 800,000,000 | | $ 800,000,000 | | | | | | | |
Deferred financing fees unamortized | | | 13,800,000 | 13,800,000 | | 13,800,000 | | | | | | | | | |
Amortized deferred financing fees | | | | 400,000 | 400,000 | 893,000 | 888,000 | | | | | | | | |
Amortization of discount on long-term debt | | | | | $ 100,000 | | $ 240,000 | | | | | | | | |
Unamortized debt discount outstanding | | | | | | | | 0 | | | | | | | |
Fair market value of debt obligations | | | 811,000,000 | 811,000,000 | | 811,000,000 | | $ 831,000,000 | | | | | | | |
Prepaid and Other Assets [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Deferred financing fees unamortized | | | 1,800,000 | 1,800,000 | | 1,800,000 | | | | | | | | | |
Other Non-Current Assets [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Deferred financing fees unamortized | | | $ 12,000,000 | $ 12,000,000 | | $ 12,000,000 | | | | | | | | | |
5.250% Senior Unsecured Notes Due 2024 [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Debt instrument interest rate | | | 5.25% | 5.25% | | 5.25% | | | | | | | | | |
Maturity date | | | | | | Nov. 20, 2024 | | | | | | | | | |
Redemption description | | | | | | At any time prior to November 15, 2019, the Company may redeem all or part of the Senior Notes upon not less than 30 nor more than 60 days' prior notice at a redemption price equal to the sum of (i) 100% of the principal amount thereof, plus (ii) a make-whole premium as of the date of redemption, plus (iii) accrued and unpaid interest and additional interest, if any, thereon, to the date of redemption. | | | | | | | | | |
Percentage of aggregate principal amount redeemed | | | | | | 35.00% | | | | | | | | | |
Redemption price | | | | | | 105.25% | | | | | | | | | |
Debt instrument description | | | | | | Interest on the Senior Notes accrues at a fixed rate of 5.25% per annum and is payable semiannually in arrears on May 15 and November 15 of each year. The first interest payment was made on May 15, 2015. The Company will make interest payments to holders of record of the Senior Notes on the immediately preceding May 1 and November 1. | | | | | | | | | |
5.250% Senior Unsecured Notes Due 2024 [Member] | Private Placement [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Debt instrument principal amount | | | | | | | | | $ 800,000,000 | | | | | | |
Debt instrument interest rate | | | | | | | | | 5.25% | | | | | | |
Term Loan [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Outstanding indebtedness, amount | | | | | | | | | $ 794,800,000 | | | | | | |
Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Bearing interest rate, percentage | | | | | | | | | 2.25% | | | | | | |
Derivatives not Designated as Hedging Instruments [Member] | Foreign Currency Forwards [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Foreign currency forwards, notional amount | | | $ 26,600,000 | $ 26,600,000 | | $ 26,600,000 | | | | | | | | | |
Revolving Credit Facility [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Revolving credit facility, maximum borrowing | | | | | | | | | $ 200,000,000 | | | | | | |
Revolving credit agreement, term | | | | | | 5 years | | | | | | | | | |
Revolving credit agreement, conditional description | | | | | | The 2014 Revolving Credit Agreement has an initial term of five years that may be extended, at the Company's request, for two additional one year terms. | | | | | | | | | |
2012 Repurchase Program [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Repurchase program authorizing the purchase of shares | | | | | | | | | | | | | | | $ 300,000,000 |
Shares repurchases, value | | | | | | | | | | | | $ 100,000,000 | | | |
Accelerated Share Repurchase Agreements Purchased, Prior to 2014, under 2012 Repurchase Program [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Shares repurchases, value | | | | | | | | | | | | | | $ 200,000,000 | |
2014 Repurchase Program [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Repurchase program authorizing the purchase of shares | | | | | | | | | | | $ 850,000,000 | | $ 300,000,000 | | |
Accelerated Share Repurchase Agreements under 2014 Repurchase Program [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Shares repurchases, value | | | | | | | | | | $ 300,000,000 | | | | | |
Common shares received | 1.2 | 4.5 | | | | | | | | | | | | | |
Accelerated share repurchase agreement, combined average price | | | | | | $ 52.79 | | | | | | | | | |
Accelerated share repurchase agreement, description | | | | | | On September 18, 2014, as part of the 2014 Repurchase Program, the Company entered into an ASR agreement to initiate share repurchases aggregating $300.0 million (the "September 2014 ASR Agreement"). As a result of the September 2014 ASR Agreement, the Company received approximately 4.5 million shares of MSCI's common stock on September 19, 2014 and approximately 1.2 million shares of MSCI's common stock on May 21, 2015 for a combined average price of $52.79 per share. | | | | | | | | | |
June 2015 10b5 1 Buyback Plan [Member] | | | | | | | | | | | | | | | |
Schedule Of Commitments And Contingencies [Line Items] | | | | | | | | | | | | | | | |
Shares repurchases, value | | | $ 62,600,000 | 62,600,000 | | $ 62,600,000 | | | | | | | | | |
Common shares received | | | 1 | | | | | | | | | | | | |
Payment of additional amount for repurchase of share | | | $ 6,700,000 | $ 6,700,000 | | $ 6,700,000 | | | | | | | | | |