Note 3 - Accumulated Other Comprehensive Income - Amounts Reclassified out of Accumulated Other Comprehensive Income by Component (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Unrealized gains on available for sale investment securities	$ 3,776,000	$ (2,000)	$ 3,990,000	$ 163,000
Income tax benefit (expense)	(1,322,000)	1,000	(1,397,000)	(57,000)
Net income	2,454,000	(1,000)	2,593,000	106,000
Total reclassifications for the period	2,454,000	(1,000)	2,593,000	106,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Income tax benefit (expense)	4,000	8,000	14,000	24,000
Net income	(9,000)	(15,000)	(27,000)	(45,000)
Prior service costs	(12,000)	(13,000)	(37,000)	(38,000)
Actuarial losses	(1,000)	(10,000)	(4,000)	(31,000)
Total before tax	(13,000)	(23,000)	(41,000)	(69,000)
Total reclassifications for the period	(9,000)	(15,000)	(27,000)	(45,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	2,445,000	(16,000)	2,566,000	61,000
Total reclassifications for the period	2,445,000	(16,000)	2,566,000	61,000
Income tax benefit (expense)	(1,560,000)	(1,439,000)	(5,510,000)	(4,213,000)
Net income	4,324,000	3,832,000	14,060,000	11,013,000
Total before tax	5,884,000	5,271,000	19,570,000	15,621,000
Total reclassifications for the period	$ 4,324,000	$ 3,832,000	$ 14,060,000	$ 11,013,000