Note 4 - Segment Reporting - Revenue (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenues		$ 375,234,000	$ 380,338,000	$ 1,068,756,000	$ 1,138,931,000
Net gains (losses) on investments and other financial instruments		17,652,000	13,009,000	42,901,000	47,462,000
Other Nonoperating Income		0	0	247,000	0
Interest Income, Related Party		(1,500,000)		(4,000,000.0)
Services Revenue, Net		33,943,000	42,509,000	93,945,000	114,565,000
Radian Group Inc.
Marketable Securities	$ 200,000,000
Radian Guaranty
Surplus Note	$ 200,000,000	300,000,000.0		300,000,000.0		$ 100,000,000.0
Related Party Transaction, Rate	3.00%
Mortgage segment
Revenues		320,013,000	317,646,000	922,040,000	956,660,000
Real Estate segment
Revenues		33,328,000	30,139,000	88,003,000	80,789,000
Accounts and notes receivable related to revenue service contracts		28,900,000		28,900,000		$ 10,800,000
Bad debt expense		0	0	0	0
All Other activities segment
Revenues		5,858,000	19,812,000	19,984,000	55,170,000
Valuation services
Services Revenue, Net		11,881,000	14,772,000	31,519,000	40,836,000
Title services
Services Revenue, Net		9,081,000	4,590,000	25,445,000	11,189,000
Asset management services
Services Revenue, Net		8,453,000	6,567,000	21,791,000	19,300,000
Real estate agent services
Services Revenue, Net		614,000	335,000	1,364,000	407,000
Mortgage services
Services Revenue, Net		3,914,000	2,340,000	10,965,000	4,856,000
All Other services
Services Revenue, Net		0	13,905,000	2,861,000	37,977,000
Operating Segments
Revenues		353,341,000	347,785,000	1,010,043,000	1,037,449,000
Intersegment Eliminations
Revenues		$ (1,617,000)	$ (268,000)	$ (4,419,000)	$ (1,150,000)