Unrecorded Unconditional Purchase Obligation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Unrecorded Unconditional Purchase Obligation [Line Items]
Total costs related to purchase obligations	$ 67,124	$ 53,247	$ 191,974	$ 106,336
Guarantor Obligations, Maximum Exposure, Undiscounted	1,534,176		1,534,176
Purchase Commitment [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Less than 1 year	172,295		172,295
1 - 3 years	381,321		381,321
3 - 5 years	355,532		355,532
More than 5 years	763,883		763,883
Total Purchase Obligations	1,673,031		1,673,031
Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,296,604		1,296,604
More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	215,935		215,935
More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	14,462		14,462
Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	7,175		7,175
Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	322,476		322,476
Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	215,884		215,884
Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	106,592		106,592
Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	910,723		910,723
Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	894,809		894,809
Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	15,913		15,913
Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1		1
Guarantees [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	300,977		300,977
Guarantees [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	185,911		185,911
Guarantees [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	93,430		93,430
Guarantees [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	14,462		14,462
Guarantees [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	7,174		7,174
Employee Related Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	151,311		151,311
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	117,542		117,542
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	33,769		33,769
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Employee Related Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	204,893		204,893
Employee Related Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	194,893		194,893
Employee Related Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	10,000		10,000
Employee Related Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Employee Related Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Environment Related Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	39,363		39,363
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	39,363		39,363
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Environment Related Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	678,943		678,943
Environment Related Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	673,076		673,076
Environment Related Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	5,867		5,867
Environment Related Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Environment Related Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Other Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	131,802		131,802
Other Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	58,979		58,979
Other Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	72,823		72,823
Other Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Other Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Other Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	26,887		26,887
Other Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	26,840		26,840
Other Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	46		46
Other Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Other Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1		1
Other Commitments [Member] | Guarantees [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	67,717		67,717
Other Commitments [Member] | Guarantees [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	35,611		35,611
Other Commitments [Member] | Guarantees [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	10,470		10,470
Other Commitments [Member] | Guarantees [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	14,462		14,462
Other Commitments [Member] | Guarantees [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	7,174		7,174
Coal Segment [Member] | Guarantees [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	233,260		233,260
Coal Segment [Member] | Guarantees [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	150,300		150,300
Coal Segment [Member] | Guarantees [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	82,960		82,960
Coal Segment [Member] | Guarantees [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Coal Segment [Member] | Guarantees [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0		0
Murray Energy [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Contractual Obligation	$ 3,000		$ 3,000