Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Current Assets:
Cash and cash equivalents	$ 33,779	$ 1,446,364	$ 36,722
Accounts receivable, net	675,570	487,240	570,618
Inventories, net	650,917	600,591	549,865
Other current assets	96,887	96,965	87,092
Total Current Assets	1,457,153	2,631,160	1,244,297
Property, plant and equipment	8,118,705	6,498,067	6,306,083
Allowances for depreciation, depletion and amortization	(3,005,279)	(2,905,254)	(2,800,823)
Net property, plant and equipment	5,113,426	3,592,813	3,505,260
Goodwill	2,401,505	2,160,290	2,160,060
Operating permits, net	435,761	439,116	437,713
Other intangibles, net	78,925	67,233	65,526
Other noncurrent assets	109,982	101,899	103,004
Total Assets	9,596,752	8,992,511	7,515,860
Current Liabilities:
Bank overdraft			3,794
Accounts payable	188,761	183,638	187,227
Accrued salaries, benefits and payroll taxes	38,870	44,255	36,202
Pension and postretirement benefits	13,089	13,652	8,802
Accrued insurance and other taxes	61,615	64,958	59,958
Current maturities of long-term debt and short-term facilities	320,046	299,909	140,037
Accrued interest	15,696	19,825	18,746
Other current liabilities	71,056	67,979	79,559
Total Current Liabilities	709,133	694,216	534,325
Long-term debt	2,898,876	2,727,294	1,641,944
Pension, postretirement and postemployment benefits	249,967	244,043	253,908
Deferred income taxes, net	644,469	410,723	663,414
Other noncurrent liabilities	238,837	233,758	221,738
Total Liabilities	4,741,282	4,310,034	3,315,329
Equity:
Common stock, par value $0.01 per share	629	628	627
Preferred stock, par value $0.01 per share
Additional paid-in capital	3,389,028	3,368,007	3,355,992
Accumulated other comprehensive loss	(125,883)	(129,104)	(125,906)
Retained earnings	1,579,674	1,440,069	967,058
Total Shareholders' Equity	4,843,448	4,679,600	4,197,771
Noncontrolling interests	12,022	2,877	2,760
Total Equity	4,855,470	4,682,477	4,200,531
Total Liabilities and Equity	$ 9,596,752	$ 8,992,511	$ 7,515,860