Supplemental Guarantor Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 49,433	$ 22,708
Additions to property and equipment	(20,739)	(38,561)
Acquisitions, net of cash acquired		(484,602)
Net cash used in investing activities	(20,739)	(523,163)
Proceeds from borrowings under revolving credit facility	143,502	624,199
Repayments of borrowings under revolving credit facility	(150,518)	(133,399)
Tax payments related to share-based compensation	(2,379)	(7,602)
Proceeds from exercises of stock options		3
Net cash (used in) provided by financing activities	(9,395)	483,201
Effect of exchange rate changes on cash	684	(1,163)
Net increase (decrease) in cash, cash equivalents and restricted cash	19,983	(18,417)
Cash, cash equivalents and restricted cash at beginning of period	99,817	105,747
Cash, cash equivalents and restricted cash at end of period	119,800	87,330
Parent [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	2,380	7,551
Tax payments related to share-based compensation	(2,379)	(7,602)
Proceeds from exercises of stock options		3
Net cash (used in) provided by financing activities	(2,379)	(7,599)
Net increase (decrease) in cash, cash equivalents and restricted cash	1	(48)
Cash, cash equivalents and restricted cash at beginning of period	89	101
Cash, cash equivalents and restricted cash at end of period	90	53
Issuer | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	300	9,038
Proceeds from borrowings under revolving credit facility	87,100	123,700
Repayments of borrowings under revolving credit facility	(87,400)	(132,900)
Net cash (used in) provided by financing activities	(300)	(9,200)
Net increase (decrease) in cash, cash equivalents and restricted cash		(162)
Cash, cash equivalents and restricted cash at beginning of period	6	7
Cash, cash equivalents and restricted cash at end of period	6	(155)
Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	54,106	1,301
Additions to property and equipment	(11,934)	(29,926)
Acquisitions, net of cash acquired		(465,123)
Net cash used in investing activities	(11,934)	(495,049)
Proceeds from borrowings under revolving credit facility	7,371	500,000
Repayments of borrowings under revolving credit facility	(10,327)
Intercompany financing	(570)
Net cash (used in) provided by financing activities	(3,526)	500,000
Effect of exchange rate changes on cash	(490)	(17)
Net increase (decrease) in cash, cash equivalents and restricted cash	38,156	6,235
Cash, cash equivalents and restricted cash at beginning of period	49,612	27,628
Cash, cash equivalents and restricted cash at end of period	87,768	33,863
Non-Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(7,353)	4,818
Additions to property and equipment	(8,805)	(8,635)
Acquisitions, net of cash acquired		(19,479)
Net cash used in investing activities	(8,805)	(28,114)
Proceeds from borrowings under revolving credit facility	49,031	499
Repayments of borrowings under revolving credit facility	(52,791)	(499)
Intercompany financing	570
Net cash (used in) provided by financing activities	(3,190)
Effect of exchange rate changes on cash	1,174	(1,146)
Net increase (decrease) in cash, cash equivalents and restricted cash	(18,174)	(24,442)
Cash, cash equivalents and restricted cash at beginning of period	50,110	78,011
Cash, cash equivalents and restricted cash at end of period	$ 31,936	$ 53,569