Debt - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended				1 Months Ended	9 Months Ended	1 Months Ended	9 Months Ended							9 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended			9 Months Ended		1 Months Ended
	Sep. 30, 2014 Credit Facility [Member]	Sep. 30, 2014 Credit Facility [Member]	Mar. 31, 2014 Credit Facility [Member]	Sep. 30, 2014 Credit Facility [Member] Senior Secured Revolving Credit Facility [Member]	Dec. 31, 2013 Credit Facility [Member] Senior Secured Revolving Credit Facility [Member]	Mar. 31, 2014 Credit Facility [Member] Minimum [Member]	Sep. 30, 2014 Credit Facility [Member] Minimum [Member]	Mar. 31, 2014 Credit Facility [Member] Maximum [Member]	Sep. 30, 2014 Credit Facility [Member] Maximum [Member] Two Quarters Following Closing of Material Acquisition [Member]	Sep. 30, 2014 Credit Facility [Member] Maximum [Member] April 1, 2014 Through September 30, 2014 [Member]	Sep. 30, 2014 Credit Facility [Member] Maximum [Member] October 1, 2014 Through December 31, 2014 [Member]	Sep. 30, 2014 Credit Facility [Member] Maximum [Member] Thereafter December 31, 2014 [Member]	Sep. 30, 2014 Credit Facility [Member] Maximum [Member] After July 2, 2014 but Prior to December 31, 2014 [Member]	Sep. 30, 2014 Credit Facility [Member] Senior Notes [Member] Two Quarters Following Closing of Material Acquisition [Member]	Sep. 30, 2014 Credit Facility [Member] Senior Notes [Member] Minimum [Member]	Sep. 30, 2014 Credit Facility [Member] LIBOR [Member] First Option [Member]	Mar. 31, 2014 Credit Facility [Member] LIBOR [Member] Second Option [Member]	Sep. 30, 2014 Credit Facility [Member] LIBOR [Member] Second Option [Member]	Mar. 31, 2014 Credit Facility [Member] LIBOR [Member] Minimum [Member] First Option [Member]	Mar. 31, 2014 Credit Facility [Member] LIBOR [Member] Maximum [Member] First Option [Member]	Mar. 31, 2014 Credit Facility [Member] Federal Funds Effective Rate [Member] Second Option [Member]	Sep. 30, 2014 Credit Facility [Member] Federal Funds Effective Rate [Member] Second Option [Member]	Sep. 30, 2014 Credit Facility [Member] Base Rate [Member] Second Option [Member]	Mar. 31, 2014 Credit Facility [Member] Base Rate [Member] Minimum [Member] Second Option [Member]	Mar. 31, 2014 Credit Facility [Member] Base Rate [Member] Maximum [Member] Second Option [Member]	Mar. 31, 2014 Swing-Line Loans [Member]	Mar. 31, 2014 Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 550,000,000																							$ 10,000,000	$ 45,000,000
Debt maturity date		Mar. 04, 2019
Amount by which maximum borrowing capacity may be increased			100,000,000
Nominal amount available under credit facility	388,100,000	388,100,000
Deferred financing costs written off	300,000
Reference rate																LIBOR		One month LIBOR				Federal funds	Agent established rate
Margin on variable reference interest rate (as a percent)																	1.00%		2.00%	3.25%	0.50%			1.00%	2.25%
Commitment fee on unused portion of revolving credit (as a percent)						0.35%		0.50%
Weighted-average interest rate				3.50%
Letters of credit outstanding				16,400,000	12,300,000
Total leverage ratio									5.00	5.5	5.00	4.50	4.50
Aggregate principal amount															$ 175,000,000
Senior leverage ratio		3.00												5.50
Combined interest charge coverage ratio							2.75