Acquisitions - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 10, 2017	Mar. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Payment to acquire business		$ (95)
Net par amount outstanding		298,243	$ 296,318
MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Cash purchase price	$ 334
Revenue since acquisition date		118
Net income since acquisition date		92
Net par amount outstanding		12,200
Acquisition related costs		6
MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Insured Financial Obligations Outstanding Principal Amount, Gross	347
Net par amount outstanding		$ 12,000
Subsidiaries [Member] | MBIA UK Insurance Limited [Member]
Business Acquisition [Line Items]
Cash expected to be acquired in acquisition	23
Business Combination, Consideration Transferred, Bond Exchanged, Fair Value	$ 334