Outstanding Exposure - Amortization Schedule of Puerto Rico Net Par Outstanding and Net Debt Service Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Estimated Net Par Amortization [Abstract]
Total	$ 275,767	$ 296,318
Estimated Net Debt Service Amortization [Abstract]
Total	416,724	437,535
Puerto Rico [Member]
Estimated Net Par Amortization [Abstract]
2017 (October 1 - December 31)	0
2018 (January 1 - March 31)	0
2018 (April 1 - June 30)	0
2018 (July 1 - September 30)	200
2018 (October 1 - December 31)	0
Subtotal 2018	200
2019	223
2020	285
2021	147
2022-2026	1,045
2027-2031	981
2032-2036	1,250
2037-2041	417
2042-2047	418
Total	4,966	$ 4,786
Estimated Net Debt Service Amortization [Abstract]
2017 (October 1 - December 31)	3
2018 (January 1 - March 31)	123
2018 (April 1 - June 30)	3
2018 (July 1 - September 30)	322
2018 (October 1 - December 31)	3
Subtotal 2018	451
2019	464
2020	516
2021	364
2022-2026	1,995
2027-2031	1,655
2032-2036	1,669
2037-2041	588
2042-2047	492
Total	$ 8,197