Fair Value (Reconciliation Of Beginning And Ending Balances For Assets Measured At Fair Value On Recurring Basis Using Significant Unobservable Inputs) (Details) (USD $) In Thousands	6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2011 Contingent Consideration [Member]	Mar. 31, 2011 Contingent Consideration [Member]	Jun. 30, 2011 Fuel Price Derivatives Price Three Months [Member]	Jun. 30, 2010 Fuel Price Derivatives Price Three Months [Member]	Jun. 30, 2011 Fuel Price Derivatives Diesel Six Months [Member]		Jun. 30, 2010 Fuel Price Derivatives Diesel Six Months [Member]
Beginning balance		$ (10,000)	$ (10,685)	$ 716	$ (3,643)		$ 2,641
Total gains or (losses) - realized/unrealized, included in earnings			5,160	1,059	(1,882)	[1]	(866)	[2]
Total gains or (losses) - realized/unrealized, purchases, issuances and settlements	(10,000)
Ending balance	$ (10,000)	$ (10,000)	$ (5,525)	$ 1,775	$ (5,525)		$ 1,775

[1] Gains and losses (realized and unrealized) included in earnings for the six months ended June 30, 2011, are reported in net realized and unrealized losses on fuel price derivatives on the condensed consolidated statements of income.

[2] Gains and losses (realized and unrealized) included in earnings for the three months ended June 30, 2010, are reported in net realized and unrealized losses on fuel price derivatives on the condensed consolidated statements of income.