Income Taxes (Schedule Of Income Taxes Calculated On Income Before Income Taxes And Provision For Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Taxes [Abstract]
Federal statutory tax rate of 35%	$ 51,825	$ 5,795	$ (31,594)
State income tax, net of federal income tax benefit	7,458	2,607	(676)
Foreign taxes in excess of (less than) U.S. statutory rate	(757)	(1,606)	2,388
Non-deductible operating expenses and tax-exempt income	113	878	2,231
Creditable foreign tax, net of foreign tax credits	925	631	246
Non-deductible goodwill impairment, write-down of an acquisition-related receivable and purchase-price adjustment	(2,351)	5,745	47,185
Fuel tax credit	(3,632)	(4,054)	(3,123)
IRS audit settlement	5,888
Other, net	160	2,576	821
Income tax provision	$ 59,629	$ 12,572	$ 17,478
Effective income tax rate	35.00%