Note 5 - Investments Unrealized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 3,129,901		$ 2,856,468
Available-for-sale Securities, Debt Securities	3,158,843		2,838,512
Available-for-sale Equity Securities, Amortized Cost Basis	176,930		1,330
Available-for-sale Securities, Equity Securities	176,808		1,330
Amortized Cost Debt and Equity Securities	3,306,831		2,857,798
Available-for-sale Securities	3,335,651		2,839,842
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	42,490		20,827
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	13,670		38,783
US government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	58,706		78,931
Available-for-sale Securities, Debt Securities	58,343		75,474
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	201		2
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	564		3,459
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	111,858		66,124
Available-for-sale Securities, Debt Securities	115,454		67,171
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	3,936		1,868
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	340		821
Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,713,237		1,463,720
Available-for-sale Securities, Debt Securities	1,735,846		1,455,628
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	30,429		14,320
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	7,820		22,412
RMBS
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	184,603		358,262
Available-for-sale Securities, Debt Securities	182,716		350,628
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	921		197
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	2,808		7,831
CMBS
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	432,124		429,057
Available-for-sale Securities, Debt Securities	435,101		428,289
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	4,075		2,255
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	1,098		3,023
Other ABS
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	596,416		433,603
Available-for-sale Securities, Debt Securities	597,864		434,728
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	2,023		2,037
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	575		912
Foreign government securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	31,457		24,771
Available-for-sale Securities, Debt Securities	32,019		24,594
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	589		148
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	27		325
Other than Securities Investment [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,500		2,000
Available-for-sale Securities, Debt Securities	1,500		2,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	0		0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0		0
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3,129,901		2,856,468
Available-for-sale Securities, Debt Securities	3,158,843		2,838,512
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	42,174		20,827
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	13,232		38,783
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	176,930	[1]	1,330	[2]
Available-for-sale Securities, Equity Securities	176,808	[1]	1,330	[2]
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	316	[1]	0	[2]
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	$ 438	[1]	$ 0	[2]

[1] Primarily consists of investments in fixed income and equity exchange-traded funds and publicly-traded business development company equities.

[2] Primarily consists of investments in Federal Home Loan Bank stock as required in connection with the memberships of Radian Guaranty and Radian Reinsurance in the FHLB.