Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 3,818	$ 8,338	$ 135,862	$ 98,801
Cash, cash equivalents and restricted cash	3,818	8,338	135,862	128,041
Supplemental Cash Flow Information [Abstract]
Cash refunds received from income taxes, net of payments	(397)	(2,799)
Cash paid for interest	27,412	30,128
Prepaid expenses and other current assets
Condensed Cash Flow Statements, Captions [Line Items]
Restricted cash equivalents	$ 0	$ 0	$ 0	$ 29,240

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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. 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. Cash equivalents include, but are not limited to, 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 of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount.

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The amount of cash received during the period as refunds for the overpayment of taxes.

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Amount of cash equivalents restricted as to withdrawal or usage. Cash equivalents include, but are not limited to, 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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