Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income	$ 11,868	$ 121,540	$ 75,256
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	58,474	45,019	36,418
Debt issuance amortization	1,401	912	680
Original issue discount amortization	382	272	209
Early extinguishment of debt	0	0	480
Deferred income taxes	(10,473)	(2,442)	(1,889)
Gain (loss) on disposal of property, plant and equipment	383	222	(162)
Deferred revenue	(16,079)	(8,508)	(4,855)
Equity-based compensation	3,857	7,487	3,039
Excess tax benefit from equity-based compensation	0	(3,813)	(1,380)
Bad debt provision	(290)	10,200	1,330
Other	(5,257)	367	(2,186)
Changes in assets and liabilities, net of effects of acquisitions:
Accounts receivable	62,465	(48,976)	(16,972)
Inventories	1,708	34	(24,377)
Prepaid expenses and other current assets	(708)	(2,158)	(2,959)
Income taxes	(5,837)	2,063	(18,179)
Accounts payable and accrued liabilities	(42,353)	51,357	1,385
Accrued interest	(2)	15	39
Liability for pension and other post-retirement benefits	1,953	(2,180)	574
Net cash provided by operating activities	61,492	171,411	46,451
Investing activities:
Capital expenditures	(53,646)	(92,609)	(60,470)
Purchase of short-term investments	0	0	(75,000)
Proceeds from Sale and Maturity of Available-for-sale Securities	53,568	0	0
Acquisition of business, net of cash acquired	0	(98,317)	0
Proceeds from sale of property, plant and equipment	127	20	357
Net cash provided by operating activities	49	(190,906)	(135,113)
Financing activities:
Dividends paid	(26,797)	(26,871)	(13,300)
Repurchase of common stock	(15,255)	(499)	0
Proceeds from options exercised	473	5,563	7,942
Excess tax benefit from equity-based compensation	0	3,813	1,380
Tax payments related to shares withheld for vested restricted stock and stock units	(794)	(614)	(166)
Advances from customers	0	100,000	0
Issuance of long-term debt	0	134,325	373,792
Repayment of long-term debt	(5,093)	(3,750)	(257,976)
Prepayment penalties	0	0	(250)
Principal payments on capital lease obligations	0	(132)	(744)
Financing fees	(64)	(2,871)	(4,051)
Net cash provided by (used in) financing activities	(47,530)	208,964	106,627
Net increase in cash and cash equivalents	14,011	189,469
Cash and cash equivalents, beginning of period	263,066	73,597	55,632
Cash and cash equivalents, end of period	277,077	263,066	$ 73,597
Non-cash financing activities:
Capital lease obligations incurred to acquire assets	0	0
Cash paid during the period for:
Interest	21,729	15,920
Taxes, net of refunds	$ 4,568	$ 37,637