Long-Term Debt - Outstanding Debt Maturities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Maturities of outstanding debt
2019	$ 24,234
2020	3,908
2021	703,708
2022	3,174
2023	403,084
Thereafter	1,263,285
Total debt	2,401,393	$ 2,408,852
Interest costs
Interest costs incurred	129,500	136,100	$ 148,500
Interest costs incurred capitalized	$ 2,900	$ 1,700	$ 2,500

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.

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Total interest costs incurred during the period and either capitalized or charged against earnings.

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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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