Note 3 - Comprehensive Income (Details) - Amounts Reclassified Out of Each Component of OCI - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains and losses on available-for-sale securities	$ (932,000)	$ (103,000)	$ (1,006,000)	$ (134,000)
Income tax provision	1,452,000	1,400,000	2,681,000	2,799,000
Net income	4,357,000	4,163,000	8,172,000	8,451,000
Amortization of defined benefit pension and postretirement items:
Total before tax	5,809,000	5,563,000	10,853,000	11,250,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(609,000)	(69,000)	(659,000)	(92,000)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gains and losses on available-for-sale securities	(932,000)	(103,000)	(1,006,000)	(134,000)
Income tax provision	326,000	36,000	352,000	47,000
Net income	(606,000)	(67,000)	(654,000)	(87,000)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax provision	2,000	2,000	3,000	3,000
Net income	(3,000)	(2,000)	(5,000)	(5,000)
Amortization of defined benefit pension and postretirement items:
Prior service cost	(8,000)	(8,000)	(15,000)	(16,000)
Actuarial loss	3,000	4,000	7,000	8,000
Total before tax	$ (5,000)	$ (4,000)	$ (8,000)	$ (8,000)