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.

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

Long-Term Debt (Senior Notes Due 2026 and 2046) (Details) - USD ($) $ in Millions	Apr. 24, 2017	Dec. 31, 2018	Dec. 31, 2017	Aug. 10, 2016
Debt Instrument [Line Items]
Principal amount		$ 2,715	$ 3,853
3.60% Senior Notes Due 2026 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount		750	750	$ 750
Exchange Offer Percentage	99.97%
5.0% 2046 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount		$ 700	$ 700	$ 700
Exchange Offer Percentage	100.00%