Variable Interest Entities Variable Interest Entities - Unpaid Principal (Details) - Variable Interest Entity, Primary Beneficiary [Member] - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
FG VIEs' assets	$ 330	$ 350
FG VIEs' liabilities with recourse	38	48
FG VIEs' liabilities without recourse	24	28
Unpaid principal balance for the FG VIEs’ assets that were over 90 days or more past due	67	71
Unpaid principal for FG VIEs’ liabilities with recourse	$ 542	$ 565