Debt - Notes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Unsecured notes	$ 5,936,335	$ 5,933,286
Debt instrument, maturity date	Jan. 10, 2022
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Aug. 01, 2047
Weighted average interest rate	4.32%
Notes Payable, Other Payables [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	2.375%
Notes Payable, Other Payables [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	7.57%

Contractual interest rate for funds borrowed, under the debt agreement.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

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- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
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-Name Accounting Standards Codification
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