Debt - Summary of Debt Instruments (Parenthetical) (Detail)	6 Months Ended	12 Months Ended	6 Months Ended					0 Months Ended	6 Months Ended	0 Months Ended	6 Months Ended			12 Months Ended	0 Months Ended	6 Months Ended		0 Months Ended						0 Months Ended		6 Months Ended
	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 Maximum [Member]	Jun. 30, 2014 Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Nov. 06, 2012 Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Jun. 22, 2011 Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Nov. 06, 2012 Term Note Payable-Domestic, June 22, 2011 [Member] Minimum [Member] USD ($)	Jun. 30, 2014 Term Note Payable-Domestic, June 22, 2011 [Member] Minimum [Member]	Nov. 06, 2012 Term Note Payable-Domestic, June 22, 2011 [Member] Maximum [Member] USD ($)	Jun. 30, 2014 Term Note Payable-Domestic, June 22, 2011 [Member] Maximum [Member]	Jun. 30, 2014 Amended and Restated [Member]	Jun. 30, 2014 Commercial Paper [Member]	Dec. 31, 2013 Commercial Paper [Member]	Nov. 06, 2012 Term Loan [Member] Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Jun. 30, 2014 Term Loan Facility [Member] Term Note Payable-Domestic, June 22, 2011 [Member]	Nov. 06, 2012 Term Loan Facility [Member] Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Mar. 20, 2013 Revolving Credit Facility [Member] Term Note Payable-Domestic, June 22, 2011 [Member]	Nov. 06, 2012 Revolving Credit Facility [Member] Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Mar. 20, 2013 Letter of Credit [Member] Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Mar. 20, 2013 Swing Line Loans [Member] Term Note Payable-Domestic, June 22, 2011 [Member] USD ($)	Mar. 20, 2013 Swing Line Loans [Member] Amended and Restated [Member] USD ($)	Mar. 20, 2013 Revolving A Facility [Member] USD ($)	Mar. 13, 2012 Revolving B Facility [Member]	Mar. 20, 2013 Revolving B Facility [Member] USD ($)	Jun. 30, 2014 Eurodollar [Member] Minimum [Member]	Jun. 30, 2014 Eurodollar [Member] Maximum [Member]	Jun. 30, 2014 New Zealand [Member] Foreign Line of Credit [Member] NZD
Debt Instrument [Line Items]
Line of credit facility, increase additional borrowings	$ 41,522,000							$ 150,000,000		$ 250,000,000					$ 250,000,000
Increase borrowing limit on revolving line of credit						850,000,000	600,000,000										550,000,000		850,000,000	20,000,000	20,000,000	110,000,000	815,000,000		35,000,000
Debt maturity date																Mar. 01, 2018		Mar. 20, 2018
United Kingdom entities as designated borrowers												Two
Line of credit facility maturity date																								5 years
Interest on the line of credit, sum of rate plus									0.25%		1.25%															1.25%	2.25%	1.00%
Principal payments on term loan					13,800,000
Percentage of quarterly commitment fees	0.25%	0.30%	0.20%	0.40%
Current purchase limit under the securitization facility	500,000,000	500,000,000
Line of credit charge													0.17%	0.17%														0.025%
Program fee variable rate													0.65%	0.675%
Acquisition	$ 10,600,000																											12,000,000
Facility, Maturity date																												Apr. 30, 2015