Consolidated Variable Interest Entities - Number of FG VIE's Consolidated (Details) - Variable Interest Entity, Primary Beneficiary [Member] $ in Millions	12 Months Ended
	Dec. 31, 2017 Entity	Dec. 31, 2016 Entity	Dec. 31, 2015 USD ($) Entity
Number of FG VIEs Consolidated [Roll Forward]
Number of FG VIE's consolidated, beginning of period	32	34	32
Number of FG VIE's, Radian Asset Acquisition	0	0	4
Number of FG VIE's consolidated	2	1	1
Number of FG VIE's deconsolidated	(2)	(2)	(1)
Number of FG VIE's matured	0	(1)	(2)
Number of FG VIE's consolidated, end of period	32	32	34
Net loss on consolidation of VIEs | $			$ (26)