CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 100,983	$ 91,050
Accounts receivable, net of allowance for doubtful accounts of $4,691 in 2018 and $4,471 in 2017	384,702	377,853
Inventories	120,944	114,866
Income taxes receivable	29,942	40,243
Prepaid expenses	6,953	8,992
Other current assets	8,558	7,131
Total current assets	652,082	640,135
Property, plant and equipment, less accumulated depreciation of $1,674,538 in 2018 and $1,659,311 in 2017	466,076	443,928
Goodwill	32,150	32,150
Other assets	30,709	31,011
Total assets	1,181,017	1,147,224
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	127,171	103,462
Accrued payroll and related expenses	26,728	23,577
Accrued insurance expenses	5,673	5,299
Accrued state, local and other taxes	9,625	8,655
Income taxes payable	8,010	3,224
Other accrued expenses	1,304	1,143
Total current liabilities	178,511	145,360
Long-term accrued insurance expenses	11,311	10,376
Long-term pension liabilities	34,818	35,635
Deferred income taxes	38,460	39,437
Other long-term liabilities	4,210	4,719
Total liabilities	267,310	235,527
Common stock	21,547	21,654
Capital in excess of par value	0	0
Retained earnings	909,185	906,745
Accumulated other comprehensive loss	(17,025)	(16,702)
Total stockholders' equity	913,707	911,697
Total liabilities and stockholders' equity	$ 1,181,017	$ 1,147,224