Note 6 - Investments Other (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Investment Holdings [Line Items]
Total investments	$ 5,153,029,000	$ 4,643,942,000
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	88,400,000
FHLB advances	82,532,000	0
Debt Securities [Member]
Investment Holdings [Line Items]
Assets Held by Insurance Regulators	$ 17,600,000	11,800,000
Minimum
Investment Holdings [Line Items]
Investment as a Percentage of Total Stockholder's Equity	10.00%
List of countries under stress due to economic uncertainty, potential restructuring and ratings downgrades \| Debt Security, Government, Non-US [Member]
Investment Holdings [Line Items]
Total investments	$ 0	$ 0

This concept represents the threshold for reporting any investment holding in an individual or affiliate.

No definition available.

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- Definition

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

+ References

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-Paragraph 1
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- Definition

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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-Section 50
-Paragraph 3
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Sum of the carrying amounts as of the balance sheet date of all investments.

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