Note 10 - Income Taxes (Details) - Components of the Income Taxes Attributable to Income from Operations and Changes in Equity (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of the Income Taxes Attributable to Income from Operations and Changes in Equity [Abstract]
Income from operations	$ 28,573	$ 22,956	$ 21,847
Equity:
Change in fair value of securities available for sale	9,200	(21,309)	5,577
Current year actuarial gains (losses) of postretirement plans	(2,880)	2,527	(340)
Amortization of net actuarial losses and prior service credits	(311)	521	436
Compensation expense for tax purposes in (excess) or less than that recognized for financial reporting purposes	(846)	(443)	303
Total income taxes	$ 33,736	$ 4,252	$ 27,823