Notes Payable and Revolving Lines of Credit - Schedule of Information on Lines of Credit (Details)	12 Months Ended
Dec. 31, 2020 USD ($) extension_option	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Amount Drawn	$ 949,000,000	$ 158,000,000
Debt Capacity	1,190,000,000
Credit Line 1
Debt Instrument [Line Items]
Amount Drawn	102,000,000
Debt Capacity	$ 140,000,000
Interest Rate	1.60%
Number of extensions available \| extension_option	1
Extension term	2 years
Credit Line 2
Debt Instrument [Line Items]
Amount Drawn	$ 487,000,000
Debt Capacity	$ 650,000,000
Interest Rate	1.00%
Number of extensions available \| extension_option	2
Extension term	6 months
Credit Line 3
Debt Instrument [Line Items]
Amount Drawn	$ 360,000,000
Debt Capacity	$ 400,000,000
Interest Rate	1.50%
Number of extensions available \| extension_option	1
Extension term	12 months
LIBOR \| Credit Line 1
Debt Instrument [Line Items]
Basis spread on variable rate	1.45%
LIBOR \| Credit Line 2
Debt Instrument [Line Items]
Basis spread on variable rate	0.90%
LIBOR \| Credit Line 3
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%

Line Of Credit Facility, Extension Term

No definition available.

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- Definition

Line Of Credit Facility, Number Of Extensions Available

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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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.

+ Details

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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- Definition

The effective interest rate at the end of the reporting period.

+ References

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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