Acquisitions - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Jan. 10, 2017	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Payment to acquire business			$ (95)
Net par amount outstanding		$ 290,620	290,620	$ 296,318
MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Cash purchase price	$ 334
Revenue since acquisition date			149
Net income since acquisition date			112
Net par amount outstanding		12,700	12,700
Acquisition related costs		$ 1	$ 7
Subsidiaries [Member] | MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Cash expected to be acquired in acquisition	23
Bond Exchanged, Fair Value	334
MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Insured Financial Obligations Outstanding Principal Amount, Gross	347
Net par amount outstanding	$ 12,000