CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 125,812	$ 131,835
Accounts receivable, net of allowance for doubtful accounts of $4,163 in 2017 and $2,553 in 2016	343,299	169,166
Inventories	112,658	108,316
Income taxes receivable	8,926	57,174
Prepaid expenses	5,410	6,718
Other current assets	5,573	5,848
Total current assets	601,678	479,057
Property, plant and equipment, less accumulated depreciation of $1,649,266 in 2017 and $1,595,508 in 2016	443,555	497,986
Goodwill	32,150	32,150
Other assets	28,502	26,259
Total assets	1,105,885	1,035,452
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	103,801	70,536
Accrued payroll and related expenses	16,882	12,130
Accrued insurance expenses	4,351	4,099
Accrued state, local and other taxes	6,641	3,094
Income taxes payable	15,206	4,929
Other accrued expenses	1,463	6,680
Total current liabilities	148,344	101,468
Long-term accrued insurance expenses	9,926	9,537
Long-term pension liabilities	34,918	32,864
Deferred income taxes	60,849	81,466
Other long-term liabilities	3,537	3,318
Total liabilities	257,574	228,653
Common stock	21,735	21,749
Capital in excess of par value
Retained earnings	844,198	803,152
Accumulated other comprehensive loss	(17,622)	(18,102)
Total stockholders' equity	848,311	806,799
Total liabilities and stockholders' equity	$ 1,105,885	$ 1,035,452

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.