UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net Income	$ 19,876	$ 38,637
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	25,288	21,426
Deferred taxes	7,713	7,777
Compensation expense related to share-based compensation plans	4,972	4,245
Loss (gain) on sale of assets	307	(255)
Excess tax benefits from share based compensation		132
Changes in operating assets and liabilities:
Restricted investments	(2,408)	1,117
Accounts receivable, net	26,240	(12,826)
Prepaid taxes	(3,352)	(2,977)
Prepaid expenses and other current assets	4,493	2,685
Other assets	(2,653)	561
Accounts payable	307	24,740
Accrued expenses	(18,013)	(14,031)
Non-current liabilities	368	1,211
Net cash provided by operating activities	63,138	72,442
Cash flows from investing activities:
Proceeds from sale of equipment	2,356	1,148
Purchases of property and equipment	(29,593)	(25,217)
Net cash used in investing activities	(27,237)	(24,069)
Cash flows from financing activities:
Proceeds from issuance of debt	16,149	13,274
Repayments of long term debt	(23,118)	(16,180)
Stock tendered for payments of withholding taxes	(3,293)	(2,379)
Purchase of treasury stock		(85,000)
Capital lease payments	(1,399)	(1,297)
Excess tax benefits from share-based compensation		(359)
Net cash used in financing activities	(11,661)	(91,941)
Effect of exchange rate changes on cash and cash equivalents	95	(31)
Net increase (decrease) in cash and cash equivalents	24,335	(43,599)
Cash and cash equivalents beginning of the period	127,404	207,749
Cash and cash equivalents end of the period	151,739	164,150
Supplemental disclosures of cash paid for:
Interest	2,176	1,762
Income taxes	$ 10,743	$ 22,399