Note 1 - Condensed Consolidated Financial Statements - Business Overview, Recent Developments and Significant Accounting Policies Current Year Developments (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	May 06, 2019	Mar. 20, 2019
First Quarter 2019 Repurchase Program
Stock Repurchase Program, Authorized Amount					$ 150.0
Total of All Repurchase Programs
Stock Repurchase Program, Authorized Amount					$ 250.0
Stock Repurchased During Period, Shares			1,546,674
Accelerated Share Repurchases, Final Price Paid Per Share			$ 20.54
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 218.2
Mortgage Insurance Segment
Risk In Force			$ 57,400.0
Subsequent Event | Total of All Repurchase Programs
Stock Repurchased During Period, Shares		4,131,329
Accelerated Share Repurchases, Final Price Paid Per Share		$ 21.94
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 127.7
Subsequent Event | Radian Guaranty
Statutory Accounting Practices, Dividends Paid with Approval of Regulatory Agency	$ 375.0
Subsequent Event | Eagle Re 2019-1 (Primary) | Mortgage Insurance Segment | Radian Guaranty
Reinsurance Retention Policy, Excess Retention, Amount Reinsured	562.0
Risk In Force	10,700.0
Proceeds from Issuance of Debt	$ 562.0