Debt and Credit Facilities - Additional Information (Detail) - USD ($)			3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Debt Instrument [Line Items]
Repayment of unsecured senior notes with proceeds from IPO			$ 100,000,000
Interest rate			4.83%
Maturity date			May 07, 2017
Total principal outstanding	$ 590,474,000	$ 684,296,000	$ 590,474,000
Revolving Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility, Outstanding borrowings	0	0	0
Revolving Credit Agreement [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, Standby letters of credit	4,100,000	4,100,000	4,100,000
Secured Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, Maximum borrowing capacity against qualifying trade receivables	200,000,000		$ 200,000,000
Credit facility, Interest rate description			We have a secured credit facility that allows us to borrow up to $200,000 against qualifying trade receivables at rates based on the 30-day LIBOR.
Secured Credit Facility [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, Standby letters of credit	$ 60,011,000	$ 60,085,000	$ 60,011,000
Trade Receivables [Member] | Collateralized [Member] | Secured Credit Facility [Member]
Debt Instrument [Line Items]
Interest rate	1.85%	1.68%
Total principal outstanding	$ 50,000,000	$ 135,000,000	$ 50,000,000