Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Financing Agreements (Details) - Loans Payable - One Point Zero Percent Windsor Property Loan - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Aug. 01, 2017	Jun. 16, 2007
Debt Instrument [Line Items]
Amount of unsecured notes issued				$ 10
Long-term debt	$ 5	$ 5
Debt Instrument, Collateral Amount			$ 5