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Line of Credit, Long-Term Debt and Capital Lease Obligations - Schedule of Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt instrument principal amount	$ 1,860,500	$ 1,713,500
Less: Current portion, principal		(20,000)
Debt instrument principal long-term portion		1,693,500
Unamortized debt issuance cost	(14,367)	(14,756)
Less: Current portion, unamortized debt issuance costs		0
Long-term portion, principal, unamortized debt issuance costs		(14,756)
Long term debt	1,846,133	1,698,744
Less: Current portion		(20,000)
Long-term portion		1,678,744
5.25% Senior Unsecured Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	750,000	750,000
Unamortized debt issuance cost	(9,503)	(11,109)
Long term debt	740,497	738,891
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	1,110,500	783,500
Unamortized debt issuance cost	(4,864)	(3,388)
Long term debt	$ 1,105,636	780,112
Term Loan Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument principal amount		180,000
Unamortized debt issuance cost		(259)
Long term debt		$ 179,741

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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-Subparagraph (SX 210.7-03(a)(16))
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