Seasonal Financing and Debt - Long-Term Debt Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	$ 0
2020	250,000
2021	350,000
2022	0
2023	250,000
Thereafter	2,050,000
Long-term debt	2,900,000	$ 3,150,000
2010 Senior Notes due October 2020 and October 2040 \| Senior Notes
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	0
2020	250,000
2021	0
2022	0
2023	0
Thereafter	250,000
Long-term debt	500,000	500,000
2011 Senior Notes due November 2041 \| Senior Notes
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Thereafter	300,000
Long-term debt	300,000	300,000
2013 Senior Notes due March 2018 and March 2023 \| Senior Notes
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	250,000
Thereafter	0
Long-term debt	250,000	500,000
2016 Senior Notes due August 2021 \| Senior Notes
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	0
2020	0
2021	350,000
2022	0
2023	0
Thereafter	0
Long-term debt	350,000	350,000
2017/2018 Senior Notes due December 2025 \| Senior Notes
Long Term Debt Maturities Repayments Of Principal [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Thereafter	1,500,000
Long-term debt	$ 1,500,000	$ 1,000,000

Long Term Debt Maturities Repayments Of Principal [Line Items]

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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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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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 next 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 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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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 third 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 second 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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