Long-Term Debt (IKE Zone Bonds) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2010
Senior Notes [Member] \| 6.5% 2035 IKE Zone Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 65	$ 65	$ 65

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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Balance Type:	credit
Period Type:	instant