Note 11 - Borrowings and Financing Activities Schedule of Senior Notes (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Senior Notes	$ 982,890	$ 1,030,348
Advances from Federal Home Loan Banks	106,382	82,532
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 Due 2020
Debt Instrument [Line Items]
Senior Notes	$ 26,852	$ 232,729
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%
Senior Notes Due 2021
Debt Instrument [Line Items]
Senior Notes	$ 69,857	$ 195,867
Debt Instrument, Interest Rate, Stated Percentage	7.00%	7.00%
Senior Notes Due 2024
Debt Instrument [Line Items]
Senior Notes	$ 443,931	$ 443,428
Debt Instrument, Interest Rate, Stated Percentage	4.50%	4.50%
Senior Notes Due 2027
Debt Instrument [Line Items]
Senior Notes	$ 442,250	$ 0
Debt Instrument, Interest Rate, Stated Percentage	4.875%	4.875%
Senior Notes \| Senior Notes Due 2027
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Debt Instrument, Basis Spread on Variable Rate	0.50%
FHLB Advances
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 72,400	$ 60,550
Long-term Debt, Maturities, Repayments of Principal in Year Two	2,991	2,991
Long-term Debt, Maturities, Repayments of Principal in Year Three	14,000	8,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	6,000	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	8,995	8,995
Long-term Debt, Maturities, Repayments of Principal after Year Five	1,996	1,996
Advances from Federal Home Loan Banks	$ 106,382	$ 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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