Segment Information (Reconciliation Of Consolidated Segment Adjusted EBITDA Expense To Operating Expense) (Details) (USD $) In Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Segment Information
Segment Adjusted EBITDA Expense	$ 289,566	[1]	$ 250,942	[1]	$ 548,886	[1]	$ 492,201	[1]
Outside coal purchases	(5,842)		(4,544)		(9,631)		(6,386)
Other income	393		304		980		154
Operating expenses (excluding depreciation, depletion and amortization)	$ 284,117		$ 246,702		$ 540,235		$ 485,969

[1] Segment Adjusted EBITDA Expense includes operating expenses, outside coal purchases and other income. Transportation expenses are excluded as these expenses are passed through to our customers and consequently we do not realize any gain or loss on transportation revenues. We review Segment Adjusted EBITDA Expense per ton for cost trends.