Business Combination (Tables)

12 Months Ended

Dec. 31, 2011

Business Combinations [Abstract]

Summary Of Purchase Price Allocation

	(In millions)
Consideration paid, net of cash acquired	$	2,894.4
Recognized amounts of net tangible and intangible assets acquired and liabilities assumed:
Restricted cash	15.5
Receivables	113.2
Inventories	91.0
Net property, plant and equipment, including mineral rights	4,582.6
Goodwill	480.3
Other assets	35.9
Accounts payable	(86.0		)
Other accrued expenses and current liabilities	(59.1		)
Debt	(604.8		)
Litigation accrual	(108.9		)
Accrued postretirement benefits	(47.7		)
Asset retirement obligation	(112.7		)
Coal supply agreements, net	(91.0		)
Deferred income taxes, net	(1,278.9		)
Other	(35.0		)
Net tangible and intangible assets acquired	$	2,894.4

Summary Of Unaudited Pro Forma

		Year Ended December 31,
		2011				2010
			(In millions)
Total revenues
As reported	$	4,285.9		$	3,186.3
Pro forma	$	4,825.6		$	4,299.9
Net income attributable to Arch Coal
As reported	$	141.7		$	158.9
Pro forma	$	113.5		$	(1.2)

Schedule Of Costs And Expenses Reflected In The Income Before Income Taxes

		(In millions)
Costs of completing the acquisition	$	31.6
Severance costs		15.8
Write off of acquired assets		7.3
Bridge financing fees		49.5
	$	104.2