Outstanding Exposure - Amortization Schedule of Puerto Rico Net Par Outstanding and Net Debt Service Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Estimated Net Par Amortization [Abstract]
Total	$ 229,375	$ 241,802
Estimated Net Debt Service Amortization [Abstract]
Total	354,612	371,586
Puerto Rico [Member]
Estimated Net Par Amortization [Abstract]
2019 (October 1 - December 31)	0
2020 (January 1 - March 31)	0
2020 (April 1 - June 30)	0
2020 (July 1 - September 30)	286
2020 (October 1 - December 31)	0
Subtotal 2020	286
2021	149
2022	139
2023	205
2024-2028	1,213
2029-2033	884
2034-2038	957
2039-2043	176
2044-2047	261
Total	4,270	$ 4,767
Estimated Net Debt Service Amortization [Abstract]
2019 (October 1 - December 31)	3
2020 (January 1 - March 31)	106
2020 (April 1 - June 30)	3
2020 (July 1 - September 30)	392
2020 (October 1 - December 31)	3
Subtotal 2020	504
2021	351
2022	332
2023	392
2024-2028	1,977
2029-2033	1,392
2034-2038	1,184
2039-2043	259
2044-2047	300
Total	$ 6,694