Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

	December 31,
E&P Property, Plant and Equipment	2016		2015
Intangible drilling cost	$	3,583,565	$	3,452,989
Proved gas properties	2,016,916		1,922,602
Unproved gas properties	1,116,282		1,421,083
Gas gathering equipment	1,138,299		1,147,173
Gas wells and related equipment	791,996		785,744
Other gas assets	190,406		125,691
Gas advance royalties	13,762		19,745
Total E&P Property, Plant and Equipment	$	8,851,226	$	8,875,027
Less: Accumulated Depreciation, Depletion and Amortization	3,106,296		2,695,674
Total E&P Property, Plant and Equipment - Net	$	5,744,930	$	6,179,353
PA Mining Operations Property, Plant and Equipment
Coal and other plant and equipment	$	2,307,668	$	2,284,103
Coal properties and surface lands	458,398		456,044
Airshafts	371,752		351,870
Mine development	326,152		326,225
Coal advance mining royalties	16,224		16,263
Leased coal lands	26,566		26,402
Total PA Mining Operations Property, Plant and Equipment	$	3,506,760	$	3,460,907
Less: Accumulated Depreciation, Depletion and Amortization	1,768,712		1,603,642
Total PA Mining Operations Property, Plant and Equipment - Net	$	1,738,048	$	1,857,265
Other Property, Plant and Equipment
Coal and other plant and equipment	$	532,919	$	569,333
Coal properties and surface lands	481,126		484,348
Airshafts	10,003		10,002
Mine development	17,988		18,073
Coal advance mining royalties	310,530		312,452
Leased coal lands	60,836		64,765
Total Other Property, Plant and Equipment	$	1,413,402	$	1,458,973
Less: Accumulated Depreciation, Depletion and Amortization	755,941		762,885
Total Other Property, Plant and Equipment - Net	$	657,461	$	696,088
Total Company Property, Plant and Equipment	$	13,771,388	$	13,794,907
Less - Total Company Accumulated Depreciation, Depletion and Amortization	5,630,949		5,062,201
Total Company Property, Plant and Equipment - Net	$	8,140,439	$	8,732,706

Schedule of Amortization Expense Per Unit of Production [Table Text Block]

	December 31,
	2016		2015
Unproved gas properties	$	1,116,282	$	1,421,083
Coal properties	195,354		258,099
Leased coal lands	36,788		44,805
Airshafts	19,693		24,674
Coal advance mining royalties	16,270		21,544
Gas advance royalties	13,762		19,745
Mine development	7,771		7,930
Total	$	1,405,920	$	1,797,880