Leases Leases - Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets and Liabilities, Lessee [Abstract]
Total lease assets	$ 259	$ 267
Operating lease liability	254	243
Finance lease liability	44	57
Total lease liabilities	298	300
Other assets [Member]
Assets and Liabilities, Lessee [Abstract]
Operating lease assets	215	215
Finance lease assets	44	52
Other liabilities [Member]
Assets and Liabilities, Lessee [Abstract]
Operating lease liability	254	243
Long-term debt [Member]
Assets and Liabilities, Lessee [Abstract]
Finance lease liability	$ 44	$ 57