Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 59,848	$ 44,024	$ 16,736
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,460	46,646	51,308
Amortization of debt issuance costs and debt discount	1,177	1,947	2,315
Losses from equity method investment	187	736	750
Debt related expenses	1,170	5,802	0
Stock-based compensation	2,784	2,288	801
Deferred taxes	(3,414)	6,504	3,407
Change in assets and liabilities:
Receivables	(6,296)	3,342	4,133
Inventories	488	1,921	2,116
Prepaid expenses and other current assets	(3,735)	895	844
Accounts payable	3,987	2,058	(1,323)
Accrued and other current liabilities	(830)	360	1,682
Other long term liabilities	(159)	(256)	(191)
Net cash provided by operating activities	101,667	116,267	82,578
Cash flows from investing activities:
Capital expenditures	(21,459)	(11,733)	(8,812)
Software purchased or developed	(583)	(414)	(1,217)
Capital contributions to equity method investment	(2,219)	(349)	(103)
Distributions from equity method investment	790	855	1,010
Net cash used in investing activities	(23,471)	(11,641)	(9,122)
Cash flows from financing activities:
Capital contribution from Lone Star Funds	0	0	29,750
Proceeds from exercise of stock options	230	20	873
Tax withholdings on share-based compensation	(240)	0	0
Proceeds from debt refinancing	545,198	275,000	0
Disbursements for debt refinancing	(545,198)	(271,988)	0
Payments of financing costs	(1,170)	(4,424)	0
Principal payments for debt	(2,052)	(26,375)	(55,000)
Payments to repurchase common stock	(54,601)	(40,277)	(48,479)
Net cash used in financing activities	(57,833)	(68,044)	(72,856)
Effect of foreign exchange rates on cash and cash equivalents	622	225	(1,498)
Net change in cash and cash equivalents	20,985	36,807	(898)
Cash, beginning of period	51,536	14,729	15,627
Cash, end of period	$ 72,521	$ 51,536	$ 14,729