Inventories (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Inventory Disclosure [Abstract]
Coal - NACoal	$ 26,306us-gaap_EnergyRelatedInventoryCoal	$ 29,576us-gaap_EnergyRelatedInventoryCoal	$ 29,521us-gaap_EnergyRelatedInventoryCoal
Mining supplies - NACoal	19,445us-gaap_OtherInventorySupplies	19,774us-gaap_OtherInventorySupplies	17,920us-gaap_OtherInventorySupplies
Total inventories at weighted average cost	45,751	49,350	47,441
Sourced inventories - HBB	104,258us-gaap_OtherInventoryPurchasedGoods	104,746us-gaap_OtherInventoryPurchasedGoods	97,322us-gaap_OtherInventoryPurchasedGoods
Retail inventories - KC	37,087us-gaap_RetailRelatedInventory	36,286us-gaap_RetailRelatedInventory	49,150us-gaap_RetailRelatedInventory
Total inventories at FIFO	141,345us-gaap_FIFOInventoryAmount	141,032us-gaap_FIFOInventoryAmount	146,472us-gaap_FIFOInventoryAmount
Inventories, net	$ 187,096us-gaap_InventoryNet	$ 190,382us-gaap_InventoryNet	$ 193,913us-gaap_InventoryNet

Carrying amount as of the balance sheet date of coal, which is a combustible rock or minerals which are extracted from the ground and used as fuel.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of FIFO (first in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

+ Details

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Balance Type:	debit
Period Type:	instant

- Details

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- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=51655945&loc=d3e3927-108312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Gross amount of components used by the entity which are bought from another entity rather than produced by the entity.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before valuation and LIFO reserves of other supplies used within the manufacturing or production process expected to be consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Inventory

-URI http://asc.fasb.org/extlink&oid=6516093

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a)(5))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of merchandise inventory held by a retailer, wholesaler, or distributor for future sale; includes packaging and other supplies used to store, transport, or present merchandise inventory.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of weighted average cost inventory present at the reporting date when inventory is valued using different valuation methods.

+ References

+ Details

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Period Type:	instant