Cash and Cash Equivalents and Short Term Investments - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	$ 929,700,000
Money market fund	18,500,000	$ 30,300,000
Term deposits	$ 294,600,000	466,600,000
Term deposits, maximum maturity period (in months)	3 months
Cash and cash equivalents	$ 311,700,000
Fixed Maturity Plans (FMPs) of mutual funds, at cost	0	15,886,000
Non current term deposits with banks	90,000	110,000
Bank of America
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits	15,500,000
Punjab National Bank and Bank of India
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits	178,100,000	13,000,000
Restricted Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Term deposits	1,040,000	$ 530,000
Indian Subsidiaries
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	881,900,000
Indian Subsidiaries | Us Dollar Denominated
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	432,300,000
Indian Subsidiaries | Indian Rupee
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalent and short term investments	$ 449,600,000