Reconciliation of Beginning and Ending Balances for Assets (Liabilities) Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level Three) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Contingent Consideration
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance							$ (313)
Included in earnings							(198)	[1]
Included in other comprehensive income							0
Purchases, issuances and settlements							0
Transfers (in)/out of Level 3							511
Ending balance			0				0
Fuel price derivatives - diesel
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(1,925)		498		(2,142)		(107)
Included in earnings	4,211	[2]	(1,015)	[2]	4,428	[1]	(410)	[1]
Included in other comprehensive income	0		0		0		0
Ending balance	$ 2,286		$ (517)		$ 2,286		$ (517)

[1] Gains and losses (realized and unrealized) associated with fuel price derivatives, included in earnings for the nine months ended September 30, 2014 and 2013, are reported in net realized and unrealized losses on fuel price derivatives on the unaudited condensed consolidated statements of income. Gains associated with contingent consideration, included in earnings for the nine months ended September 30, 2013, are reported in other expenses and loss of foreign currency transactions on the unaudited condensed consolidated statements of income.

[2] Gains and losses (realized and unrealized) associated with fuel price derivatives, included in earnings for the three months ended September 30, 2014 and 2013, are reported in net realized and unrealized losses on fuel price derivatives on the unaudited condensed consolidated statements of income.