Revolving Line of Credit - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014
Line of Credit Facility [Line Items]
Revolving credit facility, borrowing capacity	$ 150,000,000
Revolving credit facility, maximum borrowing capacity	200,000,000
Revolving credit facility maturity date	Aug. 11, 2014
Outstanding borrowings	0
Unused available borrowing capacity	148,000,000
Letters of credit, outstanding	2,000,000
Performance guarantees outstanding	29,000,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 25,000,000
Libor Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Interest rate margin over reference rate	3.75%
Libor Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Interest rate margin over reference rate	2.50%
Bank Of America's Prime Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Interest rate margin over reference rate	2.75%
Bank Of America's Prime Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Interest rate margin over reference rate	1.50%