UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 16,167	$ 10,334
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	18,599	12,522
Deferred taxes	4,714	5,279
Compensation expense related to share-based compensation plans	3,501	2,609
Gain on sale of assets	(115)	(48)
Changes in operating assets and liabilities:
Restricted investments	916	(1,436)
Accounts receivable, net	11,643	54,600
Prepaid taxes	(47)	(171)
Prepaid expenses and other current assets	6,694	2,795
Other assets	1,866	373
Accounts payable	(19,465)	(13,175)
Accrued expenses	(10,913)	(25,990)
Non-current liabilities	(386)	12
Net cash provided by operating activities	33,174	47,704
Cash flows from investing activities:
Proceeds from sale of equipment	516	1,127
Purchases of property and equipment	(22,179)	(6,625)
Net cash used in investing activities	(21,663)	(5,498)
Cash flows from financing activities:
Proceeds from issuance of debt	16,783
Repayments of long term debt	(34,300)	(11,782)
Stock tendered for payments of withholding taxes	(3,896)	(3,157)
Capital lease payments	(695)	(727)
Net cash used in financing activities	(22,108)	(15,666)
Effect of exchange rate changes on cash and cash equivalents	(30)	56
Net (decrease) increase in cash and cash equivalents	(10,627)	26,596
Cash and cash equivalents beginning of the period	28,557	127,404
Cash and cash equivalents end of the period	17,930	154,000
Supplemental disclosures of cash paid for:
Interest	2,315	1,153
Income taxes	$ 194	$ 263