Note 4 - Fair Value of Financial Instruments Fair Value Assets Liabilities by Hierarchy Level (Details) (USD $)	Mar. 31, 2013		Dec. 31, 2012
Fair Value by Hierarchy Level [Line Items]
Derivative assets	$ 6,429,000		$ 13,609,000
Derivative liabilities	430,898,000		266,873,000
VIE debt—at fair value	107,401,000		108,858,000
Fixed-maturities held to maturity	421,000		676,000
Consolidated Financial Guaranty Insurance Contracts [Member]
Fair Value by Hierarchy Level [Line Items]
Derivative liabilities	66,752,000		70,467,000
VIE debt—at fair value	96,339,000		98,983,000
Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	5,569,100,000	[1]	5,103,000,000	[2]
Derivative assets	6,400,000		13,600,000
Other Assets	96,500,000	[3]	99,200,000	[3]
Total Assets at Fair Value	5,672,000,000		5,215,800,000
Derivative liabilities	430,900,000		266,900,000
VIE debt—at fair value	107,400,000	[4]	108,900,000	[5]
Total Liabilities at Fair Value	538,300,000		375,800,000
Fair Value, Measurements, Recurring | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value by Hierarchy Level [Line Items]
Fixed-maturities held to maturity	400,000		700,000
Other invested assets fair value disclosure	50,200,000		48,700,000
US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	1,199,600,000		571,600,000
State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	689,100,000		688,000,000
Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	631,700,000		638,000,000
Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	1,453,200,000		1,373,600,000
RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	599,500,000		663,400,000
CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	299,200,000		237,300,000
Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	221,600,000		254,100,000
Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value			117,700,000
Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	144,000,000		211,900,000
Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	251,300,000	[6]	265,900,000	[6]
Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	79,900,000	[7]	81,500,000	[8]
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	1,479,700,000	[1]	874,700,000	[2]
Derivative assets	0		0
Other Assets	0	[3]	0	[3]
Total Assets at Fair Value	1,479,700,000		874,700,000
Derivative liabilities	0		0
VIE debt—at fair value	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 [Line Items]
Total Investments at Fair Value	734,100,000		137,800,000
Fair Value, Inputs, Level 1 | State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	631,700,000		638,000,000
Fair Value, Inputs, Level 1 | Corporate bonds and notes | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value			0
Fair Value, Inputs, Level 1 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 1 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	113,900,000	[6]	98,900,000	[6]
Fair Value, Inputs, Level 1 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0	[7]	0	[8]
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	3,985,200,000	[1]	4,127,600,000	[2]
Derivative assets	0		0
Other Assets	0	[3]	0	[3]
Total Assets at Fair Value	3,985,200,000		4,127,600,000
Derivative liabilities	0		0
VIE debt—at fair value	0	[4]	0	[5]
Total Liabilities at Fair Value	0		0
Fair Value, Inputs, Level 2 | Trust Preferred Securities [Member] | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	900,000		900,000
Fair Value, Inputs, Level 2 | US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	465,500,000		433,800,000
Fair Value, Inputs, Level 2 | State and municipal obligations | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	669,900,000		669,000,000
Fair Value, Inputs, Level 2 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
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 [Line Items]
Total Investments at Fair Value	1,450,500,000		1,373,600,000
Fair Value, Inputs, Level 2 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	599,500,000		663,400,000
Fair Value, Inputs, Level 2 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	296,100,000		237,300,000
Fair Value, Inputs, Level 2 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	220,100,000		252,400,000
Fair Value, Inputs, Level 2 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value			117,700,000
Fair Value, Inputs, Level 2 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	144,000,000		211,900,000
Fair Value, Inputs, Level 2 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	137,000,000	[6]	166,000,000	[6]
Fair Value, Inputs, Level 2 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	2,600,000	[7]	2,500,000	[8]
Fair Value, Inputs, Level 2 | Short Term CDs | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	1,700,000		1,600,000
Fair Value, Inputs, Level 3
Fair Value by Hierarchy Level [Line Items]
Number Of Consolidated Other Financial Guaranty Transactions	2		2
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	104,200,000	[1]	100,700,000	[2]
Derivative assets	6,400,000		13,600,000
Other Assets	96,500,000	[3]	99,200,000	[3]
Total Assets at Fair Value	207,100,000		213,500,000
Derivative liabilities	430,900,000		266,900,000
VIE debt—at fair value	107,400,000	[4]	108,900,000	[5]
Total Liabilities at Fair Value	538,300,000		375,800,000
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | NIMS [Member]
Fair Value by Hierarchy Level [Line Items]
VIE debt—at fair value	11,100,000		9,900,000
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Consolidated Financial Guaranty Insurance Contracts [Member]
Fair Value by Hierarchy Level [Line Items]
VIE debt—at fair value	96,300,000		99,000,000
Fair Value, Inputs, Level 3 | US government and agency securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
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 [Line Items]
Total Investments at Fair Value	19,200,000		19,000,000
Fair Value, Inputs, Level 3 | Money market instruments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
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 [Line Items]
Total Investments at Fair Value	2,700,000		0
Fair Value, Inputs, Level 3 | RMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | CMBS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	3,100,000		0
Fair Value, Inputs, Level 3 | Other ABS | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	1,500,000		1,700,000
Fair Value, Inputs, Level 3 | Foreign government securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value			0
Fair Value, Inputs, Level 3 | Hybrid securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	0		0
Fair Value, Inputs, Level 3 | Equity securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	400,000	[6]	1,000,000	[6]
Fair Value, Inputs, Level 3 | Other investments | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	77,300,000	[7]	79,000,000	[8]
Fair Value, Inputs, Level 3 | Lottery Annuities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	400,000		1,000,000
Fair Value, Inputs, Level 3 | Consolidated Committed Preferred Custodial Trust Securities | Fair Value, Measurements, Recurring
Fair Value by Hierarchy Level [Line Items]
Total Investments at Fair Value	$ 76,900,000		$ 78,000,000

[1] Does not include fixed-maturities held to maturity ($0.4 million) and certain other invested assets ($50.2 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 ($0.7 million) and certain other invested assets ($48.7 million), primarily invested in limited partnerships, accounted for as cost-method investments and not measured at fair value.

[3] Primarily comprising manufactured housing loan collateral related to two consolidated financial guaranty VIEs.

[4] Comprising consolidated debt related to NIMS VIEs ($11.1 million) and amounts related to financial guaranty VIEs ($96.3 million).

[5] Comprising consolidated debt related to NIMS VIEs ($9.9 million) and amounts related to financial guaranty VIEs ($99.0 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 TruPs ($0.9 million) and short-term certificates of deposit (“CDs”) ($1.7 million) included within Level II, and lottery annuities ($0.4 million) and a guaranteed investment contract held by a consolidated VIE ($76.9 million) within Level III.

[8] Comprising TruPs ($0.9 million) and short-term CDs ($1.6 million) included within Level II, and lottery annuities ($1.0 million) and a guaranteed investment contract held by a consolidated VIE ($78.0 million) within Level III.