Commitments and Contingencies Fiscal Year Maturity Schedule (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unconditional Purchase Obligation [Line Items]
Operating Leases, Rent Expense	$ 100	$ 61	$ 50
Loans and Mortgage-Related Securities [Abstract]
2019	46,227
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total	46,227
Operating Leases [Abstract]
2019	52
2020	59
2021	57
2022	58
2023	51
Thereafter	549
Total	826
Other [Abstract]
2019	90
2020	60
2021	29
2022	2
2023	0
Thereafter	0
Total	$ 181