Note 11 - Borrowings and Financing Activities Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Advances from Federal Home Loan Banks	$ 104,492		$ 82,532
Senior Notes
Debt Instrument [Line Items]
Senior Notes	886,643		1,030,348
Senior Notes \| Senior Notes Due 2019
Debt Instrument [Line Items]
Senior Notes	$ 0		$ 158,324
Debt Instrument, Interest Rate, Stated Percentage	5.50%		5.50%
Senior Notes \| Senior Notes Due 2020
Debt Instrument [Line Items]
Senior Notes	$ 0		$ 232,729
Debt Instrument, Interest Rate, Stated Percentage	5.25%		5.25%
Senior Notes \| Senior Notes Due 2021
Debt Instrument [Line Items]
Senior Notes	$ 0		$ 195,867
Debt Instrument, Interest Rate, Stated Percentage	7.00%		7.00%
Senior Notes \| Senior Notes Due 2024
Debt Instrument [Line Items]
Senior Notes	$ 444,186		$ 443,428
Debt Instrument, Interest Rate, Stated Percentage	4.50%		4.50%
Senior Notes \| Senior Notes Due 2027
Debt Instrument [Line Items]
Senior Notes	$ 442,457		$ 0
Debt Instrument, Interest Rate, Stated Percentage	4.875%	4.875%	4.875%
FHLB Advances
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 58,881
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	6,621		$ 60,550
Long-term Debt, Maturities, Repayments of Principal in Year Two	14,000		2,991
Long-term Debt, Maturities, Repayments of Principal in Year Three	9,000		8,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	8,994		0
Long-term Debt, Maturities, Repayments of Principal in Year Five	6,996		8,995
Long-term Debt, Maturities, Repayments of Principal after Year Five			1,996
Advances from Federal Home Loan Banks	$ 104,492		$ 82,532

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.

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