Quarterly report pursuant to Section 13 or 15(d)

Debt Obligations (Credit Facility - Terms under the Amended and Restated Credit Agreement) - Additional Information (Detail)

v3.7.0.1
Debt Obligations (Credit Facility - Terms under the Amended and Restated Credit Agreement) - Additional Information (Detail) - Current Credit Agreement [Member]
3 Months Ended
Mar. 31, 2017
USD ($)
Line of Credit Facility [Line Items]  
Reduction in Quanta's maximum funded debt and maximum senior debt by all cash and cash equivalents in excess of amount $ 25,000,000
Percentage of capital stock of direct foreign subsidiaries required to secure credit agreement 65.00%
Amount of availability under the credit agreement and/or cash and cash equivalents on hand that must be present to allow for cash payments of dividends and stock repurchases $ 100,000,000
Cross default provisions with debt instruments exceeding this amount $ 100,000,000
Minimum [Member]  
Line of Credit Facility [Line Items]  
Commitment fee 0.20%
Minimum [Member] | Standby Letters of Credit [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.125%
Minimum [Member] | Performance Letters of Credit [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 0.675%
Maximum [Member]  
Line of Credit Facility [Line Items]  
Commitment fee 0.40%
Maximum [Member] | Standby Letters of Credit [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 2.125%
Maximum [Member] | Performance Letters of Credit [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.275%
Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only [Member] | Minimum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.125%
Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only [Member] | Maximum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 2.125%
Excess of Base Rate Domestic Borrowings Only [Member] | Minimum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 0.125%
Excess of Base Rate Domestic Borrowings Only [Member] | Maximum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.125%
Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings [Member] | Minimum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.125%
Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings [Member] | Maximum [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 2.125%
Excess of Federal Funds Rate [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 0.50%
Excess of Euro Currency Rate [Member]  
Line of Credit Facility [Line Items]  
Debt Instrument Basis Spread On Variable Rate 1.00%