CONDENSED CONSOLIDATING FINANCIAL STATEMENTS - Condensed Consolidating Unaudited Statements Of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Schedule of Condensed Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	$ 126,084	$ 157,018
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(108,120)	(111,021)
Acquisition of the 50% noncontrolling interest in Geostream	0	(14,600)
Intercompany notes and accounts	0	0
Other investing activities, net	16,278	7,530
Net cash used in investing activities	(91,842)	(118,091)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of long-term debt	(3,573)	0
Repayment of capital lease obligations	0	(392)
Proceeds from borrowings on revolving credit facility	220,000	195,000
Repayments on revolving credit facility	(225,000)	(210,000)
Payment of deferred financing costs	0	(69)
Repurchases of common stock	(2,239)	(3,169)
Intercompany notes and accounts	0	0
Other financing activities, net	(1,240)	(1,846)
Net cash used in financing activities	(12,052)	(20,476)
Effect of changes in exchange rates on cash	6,896	212
Net increase in cash and cash equivalents	29,086	18,663
Cash and cash equivalents, beginning of period	28,306	45,949
Cash and cash equivalents, end of period	57,392	64,612
Parent Company
Schedule of Condensed Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	0	0
Acquisition of the 50% noncontrolling interest in Geostream		0
Intercompany notes and accounts	0	0
Other investing activities, net		0
Net cash used in investing activities	0	0
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of long-term debt	(3,573)
Repayment of capital lease obligations		0
Proceeds from borrowings on revolving credit facility	220,000	195,000
Repayments on revolving credit facility	(225,000)	(210,000)
Payment of deferred financing costs		(69)
Repurchases of common stock	(2,239)	(3,169)
Intercompany notes and accounts	33,381	40,620
Other financing activities, net	(1,240)	(1,846)
Net cash used in financing activities	21,329	20,536
Effect of changes in exchange rates on cash	0	0
Net increase in cash and cash equivalents	21,329	20,536
Cash and cash equivalents, beginning of period	23,115	39,617
Cash and cash equivalents, end of period	44,444	60,153
Guarantor Subsidiaries
Schedule of Condensed Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	122,697	153,757
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(104,336)	(106,800)
Acquisition of the 50% noncontrolling interest in Geostream		(14,600)
Intercompany notes and accounts	(33,381)	(40,620)
Other investing activities, net	16,278	7,530
Net cash used in investing activities	(121,439)	(154,490)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of long-term debt	0
Repayment of capital lease obligations		(392)
Proceeds from borrowings on revolving credit facility	0	0
Repayments on revolving credit facility	0	0
Payment of deferred financing costs		0
Repurchases of common stock	0	0
Intercompany notes and accounts	0	0
Other financing activities, net	0	0
Net cash used in financing activities	0	(392)
Effect of changes in exchange rates on cash	0	0
Net increase in cash and cash equivalents	1,258	(1,125)
Cash and cash equivalents, beginning of period	788	1,601
Cash and cash equivalents, end of period	2,046	476
Non-Guarantor Subsidiaries
Schedule of Condensed Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	3,387	3,261
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(3,784)	(4,221)
Acquisition of the 50% noncontrolling interest in Geostream		0
Intercompany notes and accounts	0	0
Other investing activities, net	0	0
Net cash used in investing activities	(3,784)	(4,221)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of long-term debt	0
Repayment of capital lease obligations		0
Proceeds from borrowings on revolving credit facility	0	0
Repayments on revolving credit facility	0	0
Payment of deferred financing costs		0
Repurchases of common stock	0	0
Intercompany notes and accounts	0	0
Other financing activities, net	0	0
Net cash used in financing activities	0	0
Effect of changes in exchange rates on cash	6,896	212
Net increase in cash and cash equivalents	6,499	(748)
Cash and cash equivalents, beginning of period	4,403	4,731
Cash and cash equivalents, end of period	10,902	3,983
Eliminations
Schedule of Condensed Consolidating Statement of Cash Flows [Line Items]
Net cash provided by operating activities	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	0	0
Acquisition of the 50% noncontrolling interest in Geostream		0
Intercompany notes and accounts	33,381	40,620
Other investing activities, net	0	0
Net cash used in investing activities	33,381	40,620
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of long-term debt	0
Repayment of capital lease obligations		0
Proceeds from borrowings on revolving credit facility	0	0
Repayments on revolving credit facility	0	0
Payment of deferred financing costs		0
Repurchases of common stock	0	0
Intercompany notes and accounts	(33,381)	(40,620)
Other financing activities, net	0	0
Net cash used in financing activities	(33,381)	(40,620)
Effect of changes in exchange rates on cash	0	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	$ 0	$ 0