Outstanding Insurance Exposure - Puerto Rico Net Par Outstanding (Details) - USD ($) $ in Millions			3 Months Ended
	Jun. 29, 2020	Jun. 26, 2020	Jun. 30, 2020	Dec. 31, 2019
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 231,959	$ 236,807
Insured Financial Obligations, Net Par Exposures Reassumed			118
PRHTA (Transportation revenue) [Member]
Schedule of Insured Financial Obligations [Line Items]
Certified fiscal plan, commonwealth debt service, period		5 years
PREPA [Member]
Schedule of Insured Financial Obligations [Line Items]
Certified fiscal plan, commonwealth debt service, period	5 years
PRASA (Puerto Rico Aqueduct and Sewer Authority) [Member]
Schedule of Insured Financial Obligations [Line Items]
Certified fiscal plan, commonwealth debt service, period	5 years
Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			4,388	4,270
Constitutionally Guaranteed [Member] | Puerto Rico [Member] | Commonwealth of Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			1,253	1,253
Constitutionally Guaranteed [Member] | Puerto Rico [Member] | Puerto Rico Public Buildings Authority [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			140	140
Public Corporations, Certain Revenue Potentially Subject to Clawback [Member] | Puerto Rico [Member] | PRHTA (Transportation revenue) [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			842	811
Public Corporations, Certain Revenue Potentially Subject to Clawback [Member] | Puerto Rico [Member] | PRHTA (Highway revenue) [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			515	454
Public Corporations, Certain Revenue Potentially Subject to Clawback [Member] | Puerto Rico [Member] | PRCCDA (Puerto Rico Convention Center District Authority) [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			152	152
Public Corporations, Certain Revenue Potentially Subject to Clawback [Member] | Puerto Rico [Member] | PRIFA [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			16	16
Other Public Corporations [Member] | Puerto Rico [Member] | PREPA [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			825	822
Other Public Corporations [Member] | Puerto Rico [Member] | PRASA (Puerto Rico Aqueduct and Sewer Authority) [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			373	373
Other Public Corporations [Member] | Puerto Rico [Member] | MFA [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			271	248
Other Public Corporations [Member] | Puerto Rico [Member] | University of Puerto Rico [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			1	$ 1
Vintage General Obligation Bonds [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			669
Insured Financial Obligations, Net Principal Claims Paid			383
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 165
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			74.90%
General Obligation Bonds, 2011, Series D, E and PIB [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 5
Insured Financial Obligations, Net Principal Claims Paid			6
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 1
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			73.80%
General Obligation Bonds, 2011, Series C [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 210
Insured Financial Obligations, Net Principal Claims Paid			0
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 48
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			70.40%
General Obligation Bonds, 2012 [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 369
Insured Financial Obligations, Net Principal Claims Paid			0
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 72
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			69.90%
General Obligation Bonds, 2014 [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 0
Insured Financial Obligations, Net Principal Claims Paid			0
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 0
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			65.40%
Vintage Public Buildings Authority Bonds [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 140
Insured Financial Obligations, Net Principal Claims Paid			32
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 27
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			77.60%
Public Buildings Authority Bonds, 2011 [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 0
Insured Financial Obligations, Net Principal Claims Paid			0
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 0
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			76.80%
Public Buildings Authority Bonds, 2012 [Member]
Schedule of Insured Financial Obligations [Line Items]
Total net exposure			$ 0
Insured Financial Obligations, Net Principal Claims Paid			0
Insured Financial Obligations, Net Interest Claims Paid, Amount			$ 0
Insured Financial Obligations, Base Recovery As Percent of Pre-Petition Claims			72.20%