Supplemental Guarantor/Non-Guarantor Financial Information (Details 1) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 466.5	$ 444.0	$ 551.3	$ 558.8
Accounts receivable, net	490.0	557.9
Receivables from affiliates, net	0	0
Inventories	490.9	506.7
Assets from coal trading activities, net	52.7	36.1
Deferred income taxes	106.9	66.4
Other current assets	324.4	381.6
Total current assets	1,931.4	1,992.7
Property, plant, equipment and mine development, net	10,651.1	11,082.5
Deferred income taxes	4.9	7.8
Investments and other assets	957.3	1,050.4
Notes receivable from affiliates, net	0	0
Total assets	13,544.7	14,133.4
Current liabilities
Current maturities of long-term debt	21.4	31.7
Payables to affiliates, net	0	0
Deferred income taxes		0
Liabilities from coal trading activities, net	22.4	6.1
Accounts payable and accrued expenses	1,656.5	1,737.7
Total current liabilities	1,700.3	1,775.5
Long-term debt, less current maturities	5,969.7	5,970.7
Deferred income taxes	16.0	40.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	2,263.6	2,398.4
Total liabilities	9,949.6	10,185.5
Peabody Energy Corporation stockholders' equity	3,593.6	3,908.7
Noncontrolling interests	1.5	39.2
Total stockholders' equity	3,595.1	3,947.9
Total liabilities and stockholders' equity	13,544.7	14,133.4
Parent Company [Member]
Current assets
Cash and cash equivalents	317.4	300.7	353.7	269.6
Accounts receivable, net	0.1	1.3
Receivables from affiliates, net	230.6	22.8
Inventories	0	0
Assets from coal trading activities, net	0	0
Deferred income taxes	34.7	0
Other current assets	0.4	34.5
Total current assets	583.2	359.3
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	0	16.5
Investments and other assets	10,730.1	11,394.9
Notes receivable from affiliates, net	0	0
Total assets	11,313.3	11,770.7
Current liabilities
Current maturities of long-term debt	12.0	12.0
Payables to affiliates, net	0	0
Deferred income taxes		1.9
Liabilities from coal trading activities, net	0	0
Accounts payable and accrued expenses	382.1	360.0
Total current liabilities	394.1	373.9
Long-term debt, less current maturities	5,953.4	5,959.1
Deferred income taxes	27.7	0
Notes payable to affiliates, net	1,032.6	1,032.6
Other noncurrent liabilities	311.9	496.4
Total liabilities	7,719.7	7,862.0
Peabody Energy Corporation stockholders' equity	3,593.6	3,908.7
Noncontrolling interests	0	0
Total stockholders' equity	3,593.6	3,908.7
Total liabilities and stockholders' equity	11,313.3	11,770.7
Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents	0.2	0.3	0.3	0.3
Accounts receivable, net	0	0
Receivables from affiliates, net	0	35.2
Inventories	211.6	235.1
Assets from coal trading activities, net	47.0	46.7
Deferred income taxes	62.2	61.9
Other current assets	60.1	73.7
Total current assets	381.1	452.9
Property, plant, equipment and mine development, net	4,931.7	5,055.7
Deferred income taxes	19.8	0
Investments and other assets	8.0	8.8
Notes receivable from affiliates, net	1,515.0	1,433.0
Total assets	6,855.6	6,950.4
Current liabilities
Current maturities of long-term debt	0.1	0.1
Payables to affiliates, net	203.4	0
Deferred income taxes		0
Liabilities from coal trading activities, net	9.8	0.2
Accounts payable and accrued expenses	616.9	577.7
Total current liabilities	830.2	578.0
Long-term debt, less current maturities	6.4	6.5
Deferred income taxes	0	55.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	1,566.6	1,521.8
Total liabilities	2,403.2	2,162.2
Peabody Energy Corporation stockholders' equity	4,452.4	4,788.2
Noncontrolling interests	0	0
Total stockholders' equity	4,452.4	4,788.2
Total liabilities and stockholders' equity	6,855.6	6,950.4
Non-Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents	148.9	143.0	197.3	288.9
Accounts receivable, net	489.9	559.1
Receivables from affiliates, net	0	0
Inventories	279.3	271.6
Assets from coal trading activities, net	5.7	0
Deferred income taxes	10.0	6.4
Other current assets	263.9	273.4
Total current assets	1,197.7	1,253.5
Property, plant, equipment and mine development, net	5,719.4	6,026.8
Deferred income taxes	0	7.8
Investments and other assets	684.6	762.6
Notes receivable from affiliates, net	0	0
Total assets	7,601.7	8,050.7
Current liabilities
Current maturities of long-term debt	9.3	19.6
Payables to affiliates, net	27.2	58.0
Deferred income taxes		0
Liabilities from coal trading activities, net	12.6	16.5
Accounts payable and accrued expenses	657.5	802.5
Total current liabilities	706.6	896.6
Long-term debt, less current maturities	9.9	5.1
Deferred income taxes	3.2	1.5
Notes payable to affiliates, net	482.4	400.4
Other noncurrent liabilities	385.1	380.2
Total liabilities	1,587.2	1,683.8
Peabody Energy Corporation stockholders' equity	6,013.0	6,327.7
Noncontrolling interests	1.5	39.2
Total stockholders' equity	6,014.5	6,366.9
Total liabilities and stockholders' equity	7,601.7	8,050.7
Reclassifications/Eliminations [Member]
Current assets
Cash and cash equivalents	0	0
Accounts receivable, net	0	(2.5)
Receivables from affiliates, net	(230.6)	(58.0)
Inventories	0	0
Assets from coal trading activities, net	0	(10.6)
Deferred income taxes	0	(1.9)
Other current assets	0	0
Total current assets	(230.6)	(73.0)
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	(14.9)	(16.5)
Investments and other assets	(10,465.4)	(11,115.9)
Notes receivable from affiliates, net	(1,515.0)	(1,433.0)
Total assets	(12,225.9)	(12,638.4)
Current liabilities
Current maturities of long-term debt	0	0
Payables to affiliates, net	(230.6)	(58.0)
Deferred income taxes		(1.9)
Liabilities from coal trading activities, net	0	(10.6)
Accounts payable and accrued expenses	0	(2.5)
Total current liabilities	(230.6)	(73.0)
Long-term debt, less current maturities	0	0
Deferred income taxes	(14.9)	(16.5)
Notes payable to affiliates, net	(1,515.0)	(1,433.0)
Other noncurrent liabilities	0	0
Total liabilities	(1,760.5)	(1,522.5)
Peabody Energy Corporation stockholders' equity	(10,465.4)	(11,115.9)
Noncontrolling interests	0	0
Total stockholders' equity	(10,465.4)	(11,115.9)
Total liabilities and stockholders' equity	$ (12,225.9)	$ (12,638.4)