Note 4 - Segment Reporting Schedule of Segment Reporting Information by Segment (Details) $ in Thousands				3 Months Ended									12 Months Ended						15 Months Ended	24 Months Ended		33 Months Ended	36 Months Ended
		Dec. 31, 2017 USD ($)		Dec. 31, 2017 USD ($)		Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Mar. 31, 2013	Dec. 31, 2017 USD ($)		Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)		May 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Net gains (losses) on investments and other financial instruments													$ 3,621				$ 35,693
Number of Reportable Segments | segment													2
Net premiums earned—insurance				$ 245,175		$ 236,702	$ 229,096	$ 221,800	$ 233,585	$ 238,149	$ 229,085	$ 220,950	$ 932,773		$ 921,769		915,908
Services revenue				39,703		39,571	37,802	38,027	49,905	45,877	40,263	32,849	155,103		168,894		157,216
Net investment income				33,605		32,540	30,071	31,032	28,996	28,430	28,839	27,201	127,248		113,466		81,537
Other Income													2,886		3,572		2,899
Provision for losses				35,178		35,841	17,222	46,913	54,287	55,785	49,725	42,991	135,154		202,788		198,585
Policy acquisition costs				5,871		5,554	6,123	6,729	5,579	6,119	5,393	6,389	24,277		23,480		22,424
Cost of services				23,349		27,240	25,635	28,375	33,812	29,447	27,365	23,550	104,599		114,174		93,715
Other operating expenses				65,999		64,195	68,750	68,377	62,416	62,119	63,173	57,188	267,321		244,896		242,405
Restructuring Charges				5,230		12,038	0	0					17,268		0		0
Total Operating Expenses Allocated to Subsidiaries From Parent Company													72,764		56,446		53,738
Total Interest Expense Allocated to Subsidiaries From Parent Company													44,686		52,092		35,300
Total assets		$ 5,900,881		5,900,881					5,863,174				5,900,881		5,863,174					$ 5,900,881			$ 5,900,881
Net gains on investments and other financial instruments				(1,339)		$ 2,480	$ 5,331	$ (2,851)	(38,773)	$ 7,711	$ 30,527	$ 31,286	3,621		30,751		35,693
Mortgage Insurance Segment
Segment Reporting Information [Line Items]
Intangible Assets, Net (Excluding Goodwill)		145,700		145,700									145,700							145,700			145,700
Net premiums written—insurance													818,417	[1],[2]	733,834	[3]	968,505	[4]
(Increase) decrease in unearned premiums													114,356	[1]	187,935		(52,597)
Net premiums earned—insurance													932,773		921,769		915,908
Services revenue													0
Net investment income													127,248		113,466		81,537
Other Income													2,886		3,572		2,899
Revenue Non GAAP Basis													1,062,907	[5],[6]	1,038,807	[7],[8]	1,000,344	[9],[10]
Provision for losses													136,183		204,175		198,433
Policy acquisition costs													24,277		23,480		22,424
Cost of services													0		0		0
Other operating expenses													150,975		140,624		148,619
Total Expenses Non-GAAP													311,435	[6]	368,279	[8]	369,476	[10]
Operating Income (Loss) Pretax Non GAAP Before Corporate Allocations													751,472		670,528		630,868
Total Operating Expenses Allocated to Subsidiaries From Parent Company													55,441		45,178		46,418
Total Interest Expense Allocated to Subsidiaries From Parent Company													45,016		63,439		73,402
Operating Income (Loss) Pre-Tax Non-GAAP	[11]												651,015		561,911		511,048
Total assets		5,733,918		5,733,918					5,506,338				5,733,918		5,506,338		5,290,422			5,733,918		$ 5,290,422	5,733,918
New Insurance Written													53,905,000		50,530,000		41,411,000
Revenue from Related Parties													0		0		0
Costs and Expenses, Related Party													6,730		8,355		5,924
Mortgage and Real Estate Services Segment [Member]
Segment Reporting Information [Line Items]
Net premiums written—insurance	[1],[2]												0
(Increase) decrease in unearned premiums	[1]												0
Net premiums earned—insurance													0
Services revenue													161,833		177,249		163,140
Net investment income													0		0		0
Other Income													0		0		0
Revenue Non GAAP Basis													161,833	[5],[6]	177,249	[7],[8]	163,140	[9],[10]
Provision for losses													0
Policy acquisition costs													0
Cost of services													105,812		115,369		97,256
Other operating expenses													50,969		55,815		43,515
Restructuring Charges	[12]												6,828
Total Expenses Non-GAAP													163,609	[6]	171,184	[8]	140,771	[10]
Operating Income (Loss) Pretax Non GAAP Before Corporate Allocations													(1,776)		6,065		22,369
Total Operating Expenses Allocated to Subsidiaries From Parent Company													14,319		8,533		4,823
Total Interest Expense Allocated to Subsidiaries From Parent Company													17,745		17,693		17,700
Operating Income (Loss) Pre-Tax Non-GAAP	[11]												(33,840)		(20,161)		(154)
Total assets		166,963	[13]	166,963	[13]				356,836				166,963	[13]	356,836		351,678			166,963	[13]	351,678	166,963	[13]
Revenue from Related Parties													6,730		8,355		5,924
Costs and Expenses, Related Party													0		0		0
Mortgage Insurance and Mortgage and Real Estate Services Segments [Member]
Segment Reporting Information [Line Items]
Net premiums written—insurance													818,417	[1],[2]	733,834	[3]	968,505	[4]
(Increase) decrease in unearned premiums													114,356	[1]	187,935		(52,597)
Net premiums earned—insurance													932,773		921,769		915,908
Services revenue													161,833		177,249		163,140
Net investment income													127,248		113,466		81,537
Other Income													2,886		3,572		2,899
Revenue Non GAAP Basis													1,224,740	[5],[6]	1,216,056	[7],[8]	1,163,484	[9],[10]
Provision for losses													136,183		204,175		198,433
Policy acquisition costs													24,277		23,480		22,424
Cost of services													105,812		115,369		97,256
Other operating expenses													201,944		196,439		192,134
Restructuring Charges	[12]												6,828
Total Expenses Non-GAAP													475,044	[6]	539,463	[8]	510,247	[10]
Operating Income (Loss) Pretax Non GAAP Before Corporate Allocations													749,696		676,593		653,237
Total Operating Expenses Allocated to Subsidiaries From Parent Company													69,760		53,711		51,241
Total Interest Expense Allocated to Subsidiaries From Parent Company													62,761		81,132		91,102
Operating Income (Loss) Pre-Tax Non-GAAP													617,175		541,750		510,894
Total assets		$ 5,900,881		$ 5,900,881					$ 5,863,174				$ 5,900,881		$ 5,863,174		$ 5,642,100			$ 5,900,881		$ 5,642,100	$ 5,900,881
Senior Notes [Member] | Senior Notes Due 2019 [Member]
Segment Reporting Information [Line Items]
Debt Instrument, Face Amount																									$ 300,000
Reinsurer Concentration Risk [Member] | Single Premium QSR Transaction [Member] | Radian Guaranty [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage		65.00%																	20.00%	35.00%		35.00%	35.00%
Primary Risk In Force [Member] | CALIFORNIA | Geographic Concentration Risk [Member] | Mortgage Insurance Segment
Segment Reporting Information [Line Items]
Concentration Risk, Percentage													12.40%

[1] Effective December 31, 2017, we amended the 2016 Single Premium QSR Transaction to increase the amount of ceded risk for performing loans under the agreement from 35% to 65% for the 2015 through 2017 vintages, resulting in a reduction of $145.7 million in net premiums written.

[2] Net of ceded premiums written under the QSR Transactions and the 2016 Single Premium QSR Transaction. See Note 8 for additional information.

[3] Net of ceded premiums written under the QSR Transactions and the 2016 Single Premium QSR Transaction. See Note 8 for additional information.

[4] Net of ceded premiums written under the QSR Transactions. See Note 8 for additional information.

[5] Excludes net gains on investments and other financial instruments of $3.6 million, not included in adjusted pretax operating income.

[6] Includes inter-segment revenues and expenses as follows: December 31, 2017(In thousands)Mortgage Insurance ServicesInter-segment revenues included in Services segment$— $6,730Inter-segment expenses included in Mortgage Insurance segment6,730 —

[7] Excludes net gains on investments and other financial instruments of $30.8 million, not included in adjusted pretax operating income.

[8] Includes inter-segment revenues and expenses as follows: December 31, 2016(In thousands)Mortgage Insurance ServicesInter-segment revenues included in Services segment$— $8,355Inter-segment expenses included in Mortgage Insurance segment8,355 —

[9] Excludes net gains on investments and other financial instruments of $35.7 million, not included in adjusted pretax operating income.

[10] Includes inter-segment revenues and expenses as follows: December 31, 2015(In thousands)Mortgage Insurance ServicesInter-segment revenues included in Services segment$— $5,924Inter-segment expenses included in Mortgage Insurance segment5,924 —

[11] Includes inter-segment expenses and revenues as listed in the notes to the preceding tables.

[12] Primarily includes employee severance and related benefit costs. Does not include impairment of long-lived assets, which is not a component of adjusted pretax operating income.

[13] The decrease in total assets for the Services segment at December 31, 2017, as compared to December 31, 2016, is primarily due to the impairment of goodwill and other intangible assets. See Note 7 for further details.