Note 10 - Fair Value Accounting - Reconciliation of Changes in Level 3 Balances (Details) - Reported Value Measurement [Member] - Fair Value, Measurements, Recurring [Member] - Available-for-sale Securities [Member] - Mortgage-backed Securities, Issued by Private Enterprises [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Balance, beginning of period		$ 11,794	$ 9,791
Accretion		151
Proceeds from paydowns of securities (A)	[1]	(93)	(51)
Gains realized upon sale of mortgage securities		(2,931)
Market value adjustment (B)		(1,801)	2,054
Securities transferred from Level 3 to Level 2		(7,120)
Net decrease to level 3 mortgage securities – available-for-sale		(11,794)	2,003
Balance, end of period			$ 11,794

[1] Cash received on mortgage securities with no cost basis was $2.8 million and $4.7 million during 2017 and 2016, respectively.