Indebtedness Indebtedness (Schedule of Maturities) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
2018	$ 7,768
2019	275,373
2020	5,381
2021	262,463
2022	603,611
Thereafter	1,289,178
Long-term Debt	2,443,774
Interest Paid, Net	121,000	$ 163,400	$ 211,800
Interest Paid, Capitalized	$ 18,900	$ 16,100	$ 16,800

Face Value of Debt, Maturity Total

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The amount of cash paid during the current period for interest that is capitalized.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of cash paid, after deduction of cash paid for capitalized interest, for interest. 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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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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