Severance and Leased Real Estate (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Jan. 01, 2019
Severance
Restructuring Reserve [Roll Forward]
Balance at January 1, 2019	$ 19
Accrued to expense	(1)
Payments, net	(10)
Balance at September 30, 2019	$ 8
Accounting Standards Update 2016-02
Restructuring Cost and Reserve [Line Items]
Lease obligation		$ 47

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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