Debt - Additional Information (Detail) (USD $)	12 Months Ended						12 Months Ended				3 Months Ended				12 Months Ended						12 Months Ended
	Dec. 31, 2013 BasisPoint	Dec. 31, 2012	Dec. 31, 2013 Receivables Securitization Program [Member]	Dec. 31, 2012 Receivables Securitization Program [Member]	Dec. 31, 2013 Receivables Securitization Program [Member] USR [Member]	Dec. 31, 2012 Receivables Securitization Program [Member] USR [Member]	Dec. 31, 2013 Senior Secured Notes [Member]	Dec. 31, 2013 Note Purchase Agreement 2013 [Member]	Dec. 31, 2013 2013 Swap Transaction [Member]	Dec. 31, 2012 2011 Credit Agreement [Member] Letters of Credit [Member]	Dec. 31, 2013 2013 Credit Agreement [Member]	Sep. 30, 2013 2013 Credit Agreement [Member]	Jun. 30, 2013 2013 Credit Agreement [Member]	Mar. 31, 2013 2013 Credit Agreement [Member]	Dec. 31, 2013 2013 Credit Agreement [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Minimum [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Maximum [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Unspecified [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Note Purchase Agreement Replacement [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Receivables Securitization Program [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Minimum [Member]	Dec. 31, 2013 2013 Credit Agreement [Member] Maximum [Member]	Dec. 31, 2013 Capital Lease Obligations [Member]	Dec. 31, 2013 Mortgages [Member]
Debt Instrument [Line Items]
Maturity date of debt instrument																							2015	2015
Percentage of outstanding debt priced at variable interest rates	100.00%
Effective interest rate	1.30%								3.66%
Maximum basis-point change that would not affect annual interest expense	50
Effect of 50 basis point increase or decrease in annualized interest expense, on a pre-tax basis	$ 2,700,000
Maximum amount of financing upon amendment of program	200,000,000
Maximum borrowing capacity	150,000,000										700,000,000				700,000,000
Receivables sold to Investors	355,400,000	400,200,000	355,400,000	400,200,000
Credit facility					190,700,000	150,000,000
Issuance of senior secured notes							1,000,000,000
Senior Secured notes							135,000,000	150,000,000
Maturity date of debt instrument							Oct. 15, 2014	Jan. 15, 2021
Basis spread on variable rate	1.30%							3.75%								1.00%	2.00%				1.00%	2.00%
Credit agreement expiry date															Jul. 06, 2018
Outstanding letters of credit										9,400,000	11,100,000				11,100,000
Potential maximum committed principal amount											1,050,000,000				1,050,000,000
Alternate base rate loans rates																0.00%	1.00%				0.00%	1.00%
LIBOR-based loans rate															1.25%
Alternate base rate loans rate															0.25%
Percentage of lenders fee on unutilized portion borrowing facility											4.00%	4.00%	4.00%	4.00%		0.15%	0.35%				0.15%	0.35%
Outside indebtedness permitted under facility																		300,000,000	135,000,000	200,000,000
Proceed from sale of Note	$ 15,000,000
Leverage ratio																3.00	3.50				3.00	3.50