Cash and Cash Equivalents - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013 M	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Investments original maturity to be cash equivalents (in months)	3
Cash and cash equivalent and short term investment	$ 551.8
Money market fund	25.6	29.2
Term deposits, maximum maturity period (in months)	3 months
Bank Of India
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits		18.0
Bank of India and Punjab National Bank
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits	48.7
Indian Subsidiaries
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investment	494.0
Indian Subsidiaries \| Us Dollar Denominated
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investment	77.1
Indian Subsidiaries \| Indian Rupee
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investment	$ 416.8

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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Any certificate of deposit or savings account held by a bank or other financial institution for a short-term specified period of time. Because of their short-term, time deposits are considered highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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