Insurance Premiums (Roll Forward Of Premiums Receivable) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018
Insurance Premiums [Abstract]
Premiums Receivable, Beginning balance		$ 296		$ 369
Premium Payments Received		43		74
Premiums from New Business Written		0		0
Adjustments, Changes in Expected Term of Policies		4		2
Adjustments, Accretion of Premiums Receivable Discount	[1]	7		9
Adjustments, Other		7	[2]	10	[3]
Premiums Receivable, Ending balance		$ 249		$ 296

[1] Recorded within premiums earned on MBIA’s consolidated statement of operations.

[2] Primarily relates to the write off of uncollectible premiums and to a lesser extent realized gains due to changes in foreign currency exchange rates.

[3] Primarily consists of realized gains due to changes in foreign currency exchange rates.