Fair Value Measurements - Summary of Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial assets:
Restricted cash	$ 9,886
Financial liabilities:
Long-term debt	2,210,198
Capital leases	917	$ 543
7% Senior Notes
Financial liabilities:
Long-term debt	367,854	366,859
Term Loan
Financial liabilities:
Long-term debt		406,047
New Term Loan
Financial liabilities:
Long-term debt	938,002
Carrying Amount
Financial assets:
Cash and cash equivalents	134,596	61,029
Restricted cash	13,153	2,414
Marketable securities	17,631	0
Financial liabilities:
Capital leases	917	543
Acquisition-related contingent considerations	486	496
Carrying Amount \| 7% Senior Notes
Financial liabilities:
Long-term debt	367,854	366,859
Carrying Amount \| Term Loan
Financial liabilities:
Long-term debt	0	406,047
Carrying Amount \| 6% Senior Notes
Financial liabilities:
Long-term debt	880,889	0
Carrying Amount \| New Term Loan
Financial liabilities:
Long-term debt	938,002	0
Carrying Amount \| Other long-term debt
Financial liabilities:
Long-term debt	2,531	0
Carrying Amount \| Revolving Credit Facility
Financial liabilities:
Long-term debt	0	26,977
Fair Value
Financial assets:
Cash and cash equivalents	134,596	61,029
Restricted cash	13,153	2,414
Marketable securities	17,631	0
Financial liabilities:
Capital leases	917	543
Acquisition-related contingent considerations	486	496
Fair Value \| 7% Senior Notes
Financial liabilities:
Long-term debt	400,800	397,500
Fair Value \| Term Loan
Financial liabilities:
Long-term debt	0	423,858
Fair Value \| 6% Senior Notes
Financial liabilities:
Long-term debt	914,375	0
Fair Value \| New Term Loan
Financial liabilities:
Long-term debt	956,750	0
Fair Value \| Other long-term debt
Financial liabilities:
Long-term debt	2,531	0
Fair Value \| Revolving Credit Facility
Financial liabilities:
Long-term debt	$ 0	$ 29,000

Represents the fair value contingent consideration under the business combination as of the balance sheet date.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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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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- Definition

Amount of investment in marketable security.

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Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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