Note 4 - Fair Value of Financial Instruments Fair Value Assets Liabilities by Hierarchy Level (Details) (USD $)	Mar. 31, 2012		Dec. 31, 2011
Fair Value by Hierarchy Level Assets and Liabilities
Derivative Assets	$ 16,202,000		$ 17,212,000
Derivative liabilities	202,100,000		126,006,000
VIE debt	255,234,000		228,240,000
Fixed-maturities held to maturity	2,769,000		2,748,000
Consolidated Financial Guaranty Insurance Contracts [Member]
Fair Value by Hierarchy Level Assets and Liabilities
Derivative Assets	0		0
Derivative liabilities	18,300,000		19,500,000
VIE debt	246,600,000		218,800,000
Number Of Consolidated Other Financial Guaranty Transactions	2
Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	5,530,400,000	[1]	5,719,900,000	[2]
Derivative Assets	16,200,000		17,200,000
Other Assets	101,300,000	[3]	104,000,000	[3]
Total Assets at Fair Value	5,647,900,000		5,841,100,000
Derivative liabilities	202,100,000		126,000,000
VIE debt	255,200,000	[4]	228,200,000	[5]
Total Liabilities at Fair Value	457,300,000		354,200,000
Fair Value, Measurements, Recurring | Consolidated Financial Guaranty Insurance Contracts [Member]
Fair Value by Hierarchy Level Assets and Liabilities
Number Of Consolidated Other Financial Guaranty Transactions	2		2
Fair Value, Measurements, Recurring | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value by Hierarchy Level Assets and Liabilities
Other invested assets fair value disclosure	60,300,000
US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	1,145,900,000		1,110,500,000
State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	965,100,000		1,047,500,000
Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	703,800,000		723,200,000
Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	720,200,000		700,500,000
RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	886,600,000		930,200,000
CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	216,500,000		225,800,000
CDO | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	6,400,000		5,500,000
Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	120,800,000		99,900,000
Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	109,800,000		102,900,000
Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	302,400,000		346,300,000
Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	324,100,000	[6]	269,200,000	[6]
Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	28,800,000	[7]	158,400,000	[8]
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	1,221,700,000	[1]	1,226,100,000	[2]
Derivative Assets	0		0
Other Assets	0	[3]	0	[3]
Total Assets at Fair Value	1,221,700,000		1,226,100,000
Derivative liabilities	0		0
VIE debt	0	[4]	0	[5]
Total Liabilities at Fair Value	0		0
Fair Value, Inputs, Level 1 | US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	420,200,000		386,900,000
Fair Value, Inputs, Level 1 | State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	703,800,000		723,200,000
Fair Value, Inputs, Level 1 | Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | CDO | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	97,700,000	[6]	116,000,000	[6]
Fair Value, Inputs, Level 1 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0	[7]	0	[8]
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	4,155,900,000	[1]	4,329,600,000	[2]
Derivative Assets	100,000		200,000
Other Assets	0	[3]	0	[3]
Total Assets at Fair Value	4,156,000,000		4,329,800,000
Derivative liabilities	0		0
VIE debt	0	[4]	0	[5]
Total Liabilities at Fair Value	0		0
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value by Hierarchy Level Assets and Liabilities
Fixed-maturities held to maturity	2,700,000	[9]	2,600,000	[9]
Other invested assets fair value disclosure	60,300,000	[9]	61,000,000	[9]
Fair Value, Inputs, Level 2 | US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	725,700,000		723,600,000
Fair Value, Inputs, Level 2 | State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	907,000,000		985,000,000
Fair Value, Inputs, Level 2 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 2 | Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	720,200,000		700,500,000
Fair Value, Inputs, Level 2 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	835,400,000		884,700,000
Fair Value, Inputs, Level 2 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	192,500,000		190,400,000
Fair Value, Inputs, Level 2 | CDO | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 2 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	117,100,000		97,000,000
Fair Value, Inputs, Level 2 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	109,800,000		102,900,000
Fair Value, Inputs, Level 2 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	302,200,000		341,500,000
Fair Value, Inputs, Level 2 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	224,300,000	[6]	152,400,000	[6]
Fair Value, Inputs, Level 2 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	21,700,000	[7]	151,600,000	[8]
Fair Value, Inputs, Level 2 | Commercial Paper [Member] | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	20,000,000
Fair Value, Inputs, Level 2 | Committed Preferred Securities CPS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value			150,000,000
Fair Value, Inputs, Level 2 | Short Term CDs | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	1,700,000		1,600,000
Fair Value, Inputs, Level 3
Fair Value by Hierarchy Level Assets and Liabilities
Total Level III Assets	4.80%
Total Level III Liabilities	100.00%
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	152,800,000	[1]	164,200,000	[2]
Derivative Assets	16,100,000		17,000,000
Other Assets	101,300,000	[3]	104,000,000	[3]
Total Assets at Fair Value	270,200,000		285,200,000
Derivative liabilities	202,100,000		126,000,000
VIE debt	255,200,000		228,200,000
Total Liabilities at Fair Value	457,300,000		354,200,000
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | NIMS [Member]
Fair Value by Hierarchy Level Assets and Liabilities
VIE debt	8,600,000		9,400,000
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Consolidated Financial Guaranty Insurance Contracts [Member]
Fair Value by Hierarchy Level Assets and Liabilities
VIE debt	246,600,000		218,800,000
Fair Value, Inputs, Level 3 | US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	58,100,000		62,500,000
Fair Value, Inputs, Level 3 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	51,200,000		45,500,000
Fair Value, Inputs, Level 3 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	24,000,000		35,400,000
Fair Value, Inputs, Level 3 | CDO | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	6,400,000		5,500,000
Fair Value, Inputs, Level 3 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	3,700,000		2,900,000
Fair Value, Inputs, Level 3 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	200,000		4,800,000
Fair Value, Inputs, Level 3 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	2,100,000	[6]	800,000	[6]
Fair Value, Inputs, Level 3 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	7,100,000	[7]	6,800,000	[8]
Fair Value, Inputs, Level 3 | Lottery Annuities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	1,100,000		1,600,000
Fair Value, Inputs, Level 3 | Consolidated Committed Preferred Custodial Trust Securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level Assets and Liabilities
Total Investments at Fair Value	$ 6,000,000		$ 5,200,000

[1] Does not include fixed-maturities held to maturity ($2.7 million) and other invested assets ($60.3 million), primarily invested in limited partnerships, accounted for as cost-method investments and not measured at fair value

[2] Does not include fixed-maturities held to maturity ($2.6 million) and other invested assets ($61.0 million), primarily invested in limited partnerships, accounted for as cost-method investments and not measured at fair value

[3] Comprising manufactured housing loan collateral related to two consolidated financial guaranty VIEs

[4] Comprising consolidated debt related to NIMS VIEs ($8.6 million) and amounts related to financial guaranty VIEs ($246.6 million)

[5] Comprising consolidated debt related to NIMS VIEs ($9.4 million) and amounts related to financial guaranty VIEs ($218.8 million)

[6] Comprising broadly diversified domestic equity mutual funds included within Level I and various preferred and common stocks invested across numerous companies and industries included within Levels II and III

[7] Comprising short-term commercial paper ($20.0 million) and short-term CDs ($1.7 million) included within Level II, and lottery annuities ($1.1 million) and TruPs held by consolidated VIEs ($6.0 million) included within Level III

[8] Comprising short-term commercial paper within Committed Preferred Custodial Trust Securities ("CPS") trusts ($150.0 million) and short-term CDs ($1.6 million) included within Level II, and lottery annuities ($1.6 million) and TruPs held by consolidated VIEs ($5.2 million) included within Level III

[9] Included in Level II of the fair value hierarchy