Note 5 - Investments Unrealized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands		Jun. 30, 2018		Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged		$ 122,800
Loaned securities		38,350		$ 27,964
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax				48,778
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax				16,434
Available-for-sale Securities, including Loaned Securities, Amortized Cost Basis				3,617,103
Available-for-sale Securities, including Loaned Securities				3,649,447
Available-for-sale Debt Securities, Amortized Cost Basis		3,659,311		3,426,217
Fixed-maturities available for sale—at fair value (amortized cost $3,659,311 and $3,426,217)		3,586,055		3,458,719
US government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged		10,600
Amortized Cost Debt and Equity Securities		72,811		69,667
Available-for-sale Securities		71,045	[1]	69,396
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		1		96
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		1,767		367
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities		136,649		156,587
Available-for-sale Securities		137,699		161,722
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		2,957		5,834
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		1,907		699
Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities		1,987,444		1,869,318
Available-for-sale Securities		1,933,044		1,894,886
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		4,617		33,620
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		59,017		8,052
RMBS
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged		112,200
Amortized Cost Debt and Equity Securities		249,577		189,455
Available-for-sale Securities		243,659	[2]	187,229
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		1		636
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		5,919		2,862
CMBS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities		487,805		451,595
Available-for-sale Securities		477,751		453,394
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		228		3,409
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		10,282		1,610
Other ABS
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities		694,613		672,715
Available-for-sale Securities		692,564		674,548
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		1,132		2,655
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		3,181		822
Foreign government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities		46,826		31,417
Available-for-sale Securities		46,290		32,207
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		116		823
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		652		33
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Debt and Equity Securities				3,440,754
Available-for-sale Securities	[3]			3,473,382
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		9,052		47,073
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		82,725		14,445
Available-for-sale Securities, including Loaned Securities, Amortized Cost Basis		3,675,725
Available-for-sale Securities, including Loaned Securities	[4]	3,602,052
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, including Loaned Securities, Amortized Cost Basis	[5]			176,349
Available-for-sale Securities, including Loaned Securities, Equity Securities	[3],[5]			176,065
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	[5]			1,705
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	[5]			1,989
Securities Financing Transaction, Fair Value [Member]
Schedule of Available-for-sale Securities [Line Items]
Loaned securities	[6]	38,350		27,964
Securities Financing Transaction, Fair Value [Member] | Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Loaned securities		16,000		14,700
Securities Financing Transaction, Fair Value [Member] | Corporate bonds and notes
Schedule of Available-for-sale Securities [Line Items]
Loaned securities	[6]	16,199		13,862
Securities Financing Transaction, Fair Value [Member] | Foreign government securities
Schedule of Available-for-sale Securities [Line Items]
Loaned securities	[6]	222		867
Securities Financing Transaction, Fair Value [Member] | Equity securities
Schedule of Available-for-sale Securities [Line Items]
Loaned securities	[6]	$ 21,929		$ 13,235

[1] Includes securities with a fair value of $10.6 million serving as collateral for FHLB advances.

[2] Includes securities with a fair value of $112.2 million serving as collateral for FHLB advances.

[3] Includes $14.7 million of fixed maturity securities and $13.2 million of equity securities loaned to third-party Borrowers under securities lending agreements, classified as other assets in our condensed consolidated balance sheets, as further described below.

[4] Includes $16.0 million of fixed maturity securities loaned to third-party Borrowers under securities lending agreements, classified as other assets in our condensed consolidated balance sheets, as further described below.

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

[6] Our securities loaned under securities lending agreements are reported at fair value within other assets in our condensed consolidated balance sheets. All of our securities lending agreements are classified as overnight and revolving. None of the amounts are subject to offsetting.