Line of Credit and Term Loan - Additional Information (Detail) - USD ($)					3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 02, 2017	Sep. 12, 2016	May 09, 2016	May 23, 2013	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Jul. 18, 2017
Line of Credit Facility [Line Items]
Gains/ (losses) recognized in other comprehensive income (loss)					$ 342,000	$ 0	$ 633,000	$ 0
Interest Rate Risk
Line of Credit Facility [Line Items]
Hedged interest rate risk on entire term loan					$ 300,000,000		$ 300,000,000
Derivative, Fixed Interest Rate					3.16%		3.16%
Term Loan Facility
Line of Credit Facility [Line Items]
Debt principal payment					$ 0		$ 11,250,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt principal payment					10,000,000		100,000,000
Interest Rate Swap | Term Loan Facility
Line of Credit Facility [Line Items]
Gains/ (losses) recognized in other comprehensive income (loss)					$ 300,000		$ 600,000
Senior Credit Facility
Line of Credit Facility [Line Items]
Debt interest rate description							The interest rates applicable to the Senior Credit Facility other than in respect of swing line loans are LIBOR plus 1.50% or, at the option of the Company, the Base Rate (to be defined as the highest of (x) the Federal Funds Rate [as that term is defined in the Senior Credit Facility] plus 0.50%, (y) the Bank of America prime rate, or (z) LIBOR plus 1.00%) plus 0.50%. Each swingline loan shall bear interest at the Base Rate plus 0.50%. In no event shall LIBOR be less than 0% per annum.
Senior Credit Facility | Base Rate | Option Two
Line of Credit Facility [Line Items]
Debt interest rate		0.50%
Senior Credit Facility | LIBOR | Option One
Line of Credit Facility [Line Items]
Debt interest rate		1.50%
Senior Credit Facility | LIBOR | Option Two
Line of Credit Facility [Line Items]
Debt interest rate		1.00%
Senior Credit Facility | Federal Funds Effective Swap Rate | Option Two
Line of Credit Facility [Line Items]
Debt interest rate		0.50%
Senior Credit Facility | Term Loan Facility
Line of Credit Facility [Line Items]
Line of credit, effective interest rate					2.74%		2.74%
Senior Credit Facility | $160 million of Revolving Facility
Line of Credit Facility [Line Items]
Line of credit, effective interest rate					2.74%		2.74%
Senior Credit Facility | $40 million of Revolving Facility
Line of Credit Facility [Line Items]
Line of credit, effective interest rate					2.74%		2.74%
Amended Credit Agreement
Line of Credit Facility [Line Items]
Unamortized debt issuance cost					$ 800,000		$ 800,000		$ 900,000
Amended Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Debt outstanding balance					288,200,000		288,200,000		299,900,000
Amended Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt outstanding balance					$ 99,700,000		$ 99,700,000		199,900,000
Amended Credit Agreement | Term Loan and Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt interest rate description							The interest rates under the Amended Credit Agreement were, with respect to both the revolving credit facility and the term loan, (a) for the period beginning on the First Amendment Effective Date through and including the date prior to the first anniversary of the First Amendment Effective Date, (i) the Eurodollar Rate (as that term is defined in the Amended Credit Agreement) plus 1.50% with respect to Eurodollar Rate Loans (as that term is defined in the Amended Credit Agreement) and (ii) the Base Rate (as that term is defined in the Amended Credit Agreement) plus 0.50% with respect to Base Rate Loans (as that term is defined in the amendment to the Credit Agreement), (b) for the period beginning on the first anniversary of the First Amendment Effective Date through and including the date prior to the second anniversary of the First Amendment Effective Date, (i) the Eurodollar Rate plus 1.45% with respect to Eurodollar Rate Loans and (ii) the Base Rate plus 0.45% with respect to Base Rate Loans, and (c) for the period beginning on the second anniversary of the First Amendment Effective Date and continuing thereafter, (i) the Eurodollar Rate plus 1.40% with respect to Eurodollar Rate Loans and (ii) the Base Rate plus 0.40% with respect to Base Rate Loans.
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Eurodollar | First Amendment Effective Date through to the First Anniversary
Line of Credit Facility [Line Items]
Debt interest rate			1.50%
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Eurodollar | First Anniversary of the First Amendment Effective Date through Prior to the Second Anniversary Date
Line of Credit Facility [Line Items]
Debt interest rate			1.45%
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Eurodollar | Second Anniversary of the First Amendment Effective Date and Continuing Thereafter
Line of Credit Facility [Line Items]
Debt interest rate			1.40%
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Base Rate | First Amendment Effective Date through to the First Anniversary
Line of Credit Facility [Line Items]
Debt interest rate			0.50%
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Base Rate | First Anniversary of the First Amendment Effective Date through Prior to the Second Anniversary Date
Line of Credit Facility [Line Items]
Debt interest rate			0.45%
Amended Credit Agreement | Term Loan and Revolving Credit Facility | Base Rate | Second Anniversary of the First Amendment Effective Date and Continuing Thereafter
Line of Credit Facility [Line Items]
Debt interest rate			0.40%
Swing Line Loan | Base Rate
Line of Credit Facility [Line Items]
Debt interest rate		0.50%
Swing Line Loan | Maximum | LIBOR
Line of Credit Facility [Line Items]
Debt interest rate		0.00%
Subsequent Event | Term Loan Facility
Line of Credit Facility [Line Items]
Debt principal payment	$ 3,750,000
Bank of America | Senior Credit Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity		$ 500,000,000
Bank of America | Senior Credit Facility | Maximum
Line of Credit Facility [Line Items]
Aggregate amount of Additional restricted payments										$ 50,000,000
Bank of America | Senior Credit Facility | Guarantors | Syntel India | Security and Pledge Agreement
Line of Credit Facility [Line Items]
Pledge in equity interests in Syntel India		65.00%
Bank of America | Senior Credit Facility | Term Loan Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity		$ 300,000,000
Debt maturity period		5 years
Maturity date of debt instrument		Sep. 11, 2021
Bank of America | Senior Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity		$ 200,000,000
Debt maturity period		5 years
Maturity date of debt instrument		Sep. 11, 2021
Bank of America | Credit Agreement
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity				$ 150,000,000
Bank of America | Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity				$ 60,000,000
Debt maturity period				3 years
Maturity date of debt instrument				May 23, 2016
Repayments of debt									$ 190,000,000
Bank of America | Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity				$ 90,000,000
Debt maturity period				3 years
Maturity date of debt instrument				May 23, 2016
Bank of America | Amended Credit Agreement
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity			$ 200,000,000
Bank of America | Amended Credit Agreement | Guarantors | Syntel India | Security and Pledge Agreement
Line of Credit Facility [Line Items]
Pledge in equity interests in Syntel India			65.00%
Bank of America | Amended Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity			$ 100,000,000
Maturity date of debt instrument			May 09, 2019
Additional debt borrowing capacity			$ 40,000,000
Bank of America | Amended Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt maximum borrowing capacity			$ 100,000,000
Maturity date of debt instrument			May 09, 2019
Additional debt borrowing capacity			$ 10,000,000