Note 12 - Borrowings and Financing Activities Schedule of Senior Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Senior Notes Due 2019
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.50%	5.50%
Senior Notes Due 2020
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%
Senior Notes Due 2021
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.00%	7.00%
Senior Notes Due 2024
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.50%	4.50%
Senior Notes Due 2027
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%	4.875%
Senior Notes
Debt Instrument [Line Items]
Senior Notes	$ 887,110	$ 1,030,348
Senior Notes \| Senior Notes Due 2019
Debt Instrument [Line Items]
Senior Notes	0	158,324
Senior Notes \| Senior Notes Due 2020
Debt Instrument [Line Items]
Senior Notes	0	232,729
Senior Notes \| Senior Notes Due 2021
Debt Instrument [Line Items]
Senior Notes	0	195,867
Senior Notes \| Senior Notes Due 2024
Debt Instrument [Line Items]
Senior Notes	$ 444,445	443,428
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Senior Notes \| Senior Notes Due 2027
Debt Instrument [Line Items]
Senior Notes	$ 442,665	0
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 0
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	79,002	60,550
Long-term Debt, Maturities, Repayments of Principal in Year Two	19,000	2,991
Long-term Debt, Maturities, Repayments of Principal in Year Three	11,925	8,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	14,994	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	9,954	8,995
Long-term Debt, Maturities, Repayments of Principal after Year Five		1,996
Advances from Federal Home Loan Banks	$ 134,875	$ 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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