Outstanding Exposure - Amortization Schedule of Puerto Rico BIG Net Par Outstanding and BIG Net Debt Service Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Estimated BIG Net Par Amortization [Abstract]
Net Par Outstanding	$ 241,802	$ 264,952
Estimated BIG Net Debt Service Amortization [Abstract]
Total	371,586	401,118
Puerto Rico [Member]
Estimated BIG Net Par Amortization [Abstract]
2019 (January 1 - March 31)	0
2019 (April 1 - June 30)	0
2019 (July 1 - September 30)	224
2019 (October 1 - December 31)	0
Subtotal 2019	224
2020	285
2021	147
2022	137
2023	206
2024-2028	1,205
2029-2033	904
2034-2038	968
2039-2043	430
2044-2047	261
Net Par Outstanding	4,767	$ 4,966
Estimated BIG Net Debt Service Amortization [Abstract]
2019 (January 1 - March 31)	117
2019 (April 1 - June 30)	3
2019 (July 1 - September 30)	341
2019 (October 1 - December 31)	3
Subtotal 2019	464
2020	516
2021	364
2022	345
2023	408
2024-2028	2,043
2029-2033	1,487
2034-2038	1,260
2039-2043	556
2044-2047	300
Total	$ 7,743