Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net income (loss)	$ (10,660)	$ 14,823
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	14,556	13,243
Debt issuance amortization	348	352
Original issue discount amortization	96	96
Deferred income taxes	(8,563)	(3,101)
Deferred revenue	(1,250)	(5,498)
Gain (loss) on disposal of property, plant and equipment	8	(32)
Equity-based compensation	1,906	2,090
Excess tax benefit from equity-based compensation	0	(6)
Bad debt provision net of recoveries	150	3,183
Other	653	(552)
Changes in operating assets and liabilities:
Accounts receivable	(522)	21,343
Inventories	(2,087)	1,677
Prepaid expenses and other current assets	(454)	(1,512)
Income taxes	5,644	5,742
Accounts payable and accrued liabilities	(4,398)	(33,071)
Accrued interest	(1)	0
Liability for pension and other post-retirement benefits	820	1,007
Net cash provided by (used in) operating activities	(3,754)	19,784
Investing activities:
Capital expenditures	(6,068)	(13,377)
Maturities of short-term investments	15,020	0
Proceeds from sale of property, plant and equipment	58	72
Net cash provided by (used in) investing activities	9,010	(13,305)
Financing activities:
Dividends paid	(3,388)	(6,758)
Repurchase of common stock	0	(15,255)
Proceeds from Issuance of Common Stock	200,000	0
Payments of Stock Issuance Costs	(13,798)	0
Proceeds from options exercised	22	43
Excess tax benefit from equity-based compensation	0	6
Tax payments related to shares withheld for vested restricted stock	(499)	(443)
Repayment of long-term debt	(1,275)	(1,275)
Payments of Financing Costs	0	(64)
Net cash provided by (used in) financing activities	181,062	(23,746)
Net increase (decrease) in cash and cash equivalents	186,318	(17,267)
Cash and cash equivalents, beginning of period	277,077	263,066
Cash and cash equivalents, end of period	463,395	245,799
Cash paid (received) during the period for:
Interest	5,298	5,529
Taxes, net of refunds	$ (5,574)	$ 805