Outstanding Insurance Exposure - Amortization Schedule of Puerto Rico Net Par Outstanding and Net Debt Service Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Estimated Net Par Amortization [Abstract]
Total	$ 230,898	$ 236,807
Estimated Net Debt Service Amortization [Abstract]
Total	363,893	374,130
Puerto Rico [Member]
Estimated Net Par Amortization [Abstract]
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	222
2025-2029	1,158
2030-2034	1,021
2035-2039	740
2040-2044	104
2045-2047	246
Total	4,270	$ 4,270
Estimated Net Debt Service Amortization [Abstract]
2020 (April 1 - June 30)	3
2020 (July 1 - September 30)	392
2020 (October 1 - December 31)	3
Subtotal 2020	398
2021	351
2022	332
2023	392
2024	398
2025-2029	1,862
2030-2034	1,484
2035-2039	917
2040-2044	179
2045-2047	272
Total	$ 6,585