Cash and Cash Equivalents and Short Term Investments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	$ 808,700,000
Term deposits, maximum maturity period (in months)	3 months
Term deposits	367,600,000	340,300,000
Fixed Maturity Plans (FMPs) of mutual funds, at cost	16,354,000
Non current term deposits with banks	0	160,000
JPMorgan Chase Bank NA
Restricted Cash and Cash Equivalents Items [Line Items]
Money market fund	26,900,000	33,200,000
Bank of America
Restricted Cash and Cash Equivalents Items [Line Items]
Money market fund	4,000,000
Punjab National Bank
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits	100,800,000
Punjab National Bank and Bank of India
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits		29,800,000
Indian Subsidiaries
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	757,500,000
Indian Subsidiaries | Us Dollar Denominated
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	154,600,000
Indian Subsidiaries | Indian Rupee
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	$ 602,900,000