Supplemental Guarantor/Non-Guarantor Financial Information (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 508.1	$ 444.0	$ 629.5	$ 558.8
Accounts receivable, net	454.4	557.9
Receivables from affiliates, net	0	0
Inventories	549.4	506.7
Assets from coal trading activities, net	50.2	36.1
Deferred income taxes	64.2	66.4
Other current assets	283.9	381.6
Total current assets	1,910.2	1,992.7
Property, plant, equipment and mine development, net	10,855.4	11,082.5
Deferred income taxes	62.3	7.8
Investments and other assets	1,017.2	1,050.4
Notes receivable from affiliates, net	0	0
Total assets	13,845.1	14,133.4
Current liabilities
Current maturities of long-term debt	20.8	31.7
Payables to affiliates, net	0	0
Deferred income taxes	7.3	0
Liabilities from coal trading activities, net	11.6	6.1
Accounts payable and accrued expenses	1,559.9	1,737.7
Total current liabilities	1,599.6	1,775.5
Long-term debt, less current maturities	5,977.4	5,970.7
Deferred income taxes	31.1	40.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	2,221.3	2,398.4
Total liabilities	9,829.4	10,185.5
Peabody Energy Corporation stockholders' equity	3,972.9	3,908.7
Noncontrolling interests	42.8	39.2
Total stockholders' equity	4,015.7	3,947.9
Total liabilities and stockholders' equity	13,845.1	14,133.4
Parent Company [Member]
Current assets
Cash and cash equivalents	296.6	300.7	332.5	269.6
Accounts receivable, net	0.8	1.3
Receivables from affiliates, net	687.5	68.4
Inventories	0	0
Assets from coal trading activities, net	0	0
Deferred income taxes	27.0	0
Other current assets	4.2	34.5
Total current assets	1,016.1	404.9
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	0	16.5
Investments and other assets	10,612.7	11,394.9
Notes receivable from affiliates, net	0	0
Total assets	11,628.8	11,816.3
Current liabilities
Current maturities of long-term debt	12.0	12.0
Payables to affiliates, net	0	0
Deferred income taxes	0	1.9
Liabilities from coal trading activities, net	0	0
Accounts payable and accrued expenses	312.1	360.0
Total current liabilities	324.1	373.9
Long-term debt, less current maturities	5,957.2	5,959.1
Deferred income taxes	16.7	0
Notes payable to affiliates, net	1,078.2	1,078.2
Other noncurrent liabilities	279.7	496.4
Total liabilities	7,655.9	7,907.6
Peabody Energy Corporation stockholders' equity	3,972.9	3,908.7
Noncontrolling interests	0	0
Total stockholders' equity	3,972.9	3,908.7
Total liabilities and stockholders' equity	11,628.8	11,816.3
Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents	0.2	0.3	0.2	0.3
Accounts receivable, net	16.3	0
Receivables from affiliates, net	0	0
Inventories	236.0	235.1
Assets from coal trading activities, net	45.8	46.7
Deferred income taxes	61.9	61.9
Other current assets	25.8	73.7
Total current assets	386.0	417.7
Property, plant, equipment and mine development, net	4,985.3	5,055.7
Deferred income taxes	0	0
Investments and other assets	8.7	8.8
Notes receivable from affiliates, net	1,534.6	1,478.6
Total assets	6,914.6	6,960.8
Current liabilities
Current maturities of long-term debt	0.1	0.1
Payables to affiliates, net	617.1	10.4
Deferred income taxes	0	0
Liabilities from coal trading activities, net	2.0	0.2
Accounts payable and accrued expenses	516.9	577.7
Total current liabilities	1,136.1	588.4
Long-term debt, less current maturities	6.4	6.5
Deferred income taxes	40.9	55.9
Notes payable to affiliates, net	0	0
Other noncurrent liabilities	1,561.9	1,521.8
Total liabilities	2,745.3	2,172.6
Peabody Energy Corporation stockholders' equity	4,169.3	4,788.2
Noncontrolling interests	0	0
Total stockholders' equity	4,169.3	4,788.2
Total liabilities and stockholders' equity	6,914.6	6,960.8
Non-Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents	211.3	143.0	296.8	288.9
Accounts receivable, net	437.3	559.1
Receivables from affiliates, net	0	0
Inventories	313.4	271.6
Assets from coal trading activities, net	4.4	0
Deferred income taxes	4.2	6.4
Other current assets	253.9	273.4
Total current assets	1,224.5	1,253.5
Property, plant, equipment and mine development, net	5,870.1	6,026.8
Deferred income taxes	62.3	7.8
Investments and other assets	743.7	762.6
Notes receivable from affiliates, net	0	0
Total assets	7,900.6	8,050.7
Current liabilities
Current maturities of long-term debt	8.7	19.6
Payables to affiliates, net	70.4	58.0
Deferred income taxes	7.3	0
Liabilities from coal trading activities, net	9.6	16.5
Accounts payable and accrued expenses	730.9	802.5
Total current liabilities	826.9	896.6
Long-term debt, less current maturities	13.8	5.1
Deferred income taxes	2.4	1.5
Notes payable to affiliates, net	456.4	400.4
Other noncurrent liabilities	379.7	380.2
Total liabilities	1,679.2	1,683.8
Peabody Energy Corporation stockholders' equity	6,178.6	6,327.7
Noncontrolling interests	42.8	39.2
Total stockholders' equity	6,221.4	6,366.9
Total liabilities and stockholders' equity	7,900.6	8,050.7
Reclassifications/Eliminations [Member]
Current assets
Cash and cash equivalents	0	0
Accounts receivable, net	0	(2.5)
Receivables from affiliates, net	(687.5)	(68.4)
Inventories	0	0
Assets from coal trading activities, net	0	(10.6)
Deferred income taxes	(28.9)	(1.9)
Other current assets	0	0
Total current assets	(716.4)	(83.4)
Property, plant, equipment and mine development, net	0	0
Deferred income taxes	0	(16.5)
Investments and other assets	(10,347.9)	(11,115.9)
Notes receivable from affiliates, net	(1,534.6)	(1,478.6)
Total assets	(12,598.9)	(12,694.4)
Current liabilities
Current maturities of long-term debt	0	0
Payables to affiliates, net	(687.5)	(68.4)
Deferred income taxes	0	(1.9)
Liabilities from coal trading activities, net	0	(10.6)
Accounts payable and accrued expenses	0	(2.5)
Total current liabilities	(687.5)	(83.4)
Long-term debt, less current maturities	0	0
Deferred income taxes	(28.9)	(16.5)
Notes payable to affiliates, net	(1,534.6)	(1,478.6)
Other noncurrent liabilities	0	0
Total liabilities	(2,251.0)	(1,578.5)
Peabody Energy Corporation stockholders' equity	(10,347.9)	(11,115.9)
Noncontrolling interests	0	0
Total stockholders' equity	(10,347.9)	(11,115.9)
Total liabilities and stockholders' equity	$ (12,598.9)	$ (12,694.4)