Note 2 - Accumulated Other Comprehensive Income (Details) - Amounts Reclassified out of Accumulated Other Comprehensive Income by Component (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (1,737)	$ (1,283)	$ (1,959)	$ (1,120)	$ (1,135)	$ (855)	$ (1,127)	$ (1,318)	$ (6,099)	$ (4,435)	$ (2,910)
Net of tax	3,781	3,657	4,261	2,833	2,582	2,546	3,060	3,307	14,532	11,495	10,227
	5,895	5,390	6,783	4,490	4,207	3,890	4,674	5,110	22,558	17,881	15,059
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains and losses on available for sale investment securities									(97)	65
Income tax expense									34	(23)
Net of tax									(63)	42
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense									49	94
Net of tax									(91)	(175)
Prior service costs									(207)	(257)
Actuarial gains (losses)									67	(12)
									(140)	(269)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax									$ (154)	$ (133)