Note 3 - Comprehensive Income (Details) - Components of Other Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Unrealized losses on available-for-sale securities:
Unrealized holding gains on available-for-sale securities, before tax amount	$ (4,572)	$ 4,523	$ (847)	$ 9,857
Unrealized holding gains on available-for-sale securities, income tax effect	1,601	(1,582)	297	(3,450)
Unrealized holding gains on available-for-sale securities, net of tax amount	(2,971)	2,941	(550)	6,407
Reclassification adjustment for (gains) realized in income, before tax amount	(932)	(103)	(1,006)	(134)
Reclassification adjustment for (gains) realized in income, income tax effect	326	36	352	47
Reclassification adjustment for (gains) realized in income, net of tax amount	(606)	(67)	(654)	(87)
Other comprehensive gain on available-for-sale securities, before tax amount	(5,504)	4,420	(1,853)	9,723
Other comprehensive gain on available-for-sale securities, income tax effect	1,927	(1,546)	649	(3,403)
Other comprehensive gain on available-for-sale securities, net of tax amount	(3,577)	2,874	(1,204)	6,320
Unfunded pension and postretirement obligations:
Changes from plan amendments and actuarial gains and losses included in other comprehensive income, before tax amount	0	3	(100)	144
Changes from plan amendments and actuarial gains and losses included in other comprehensive income, income tax effect	0	(1)	35	(50)
Changes from plan amendments and actuarial gains and losses included in other comprehensive income, net of tax amount	0	2	(65)	94
Amortization of net transition obligation, prior service cost and net actuarial loss included in net periodic benefit cost, before tax amount	(5)	(4)	(8)	(8)
Amortization of net transition obligation, prior service cost and net actuarial loss included in net periodic benefit cost, income tax effect	2	2	3	3
Amortization of net transition obligation, prior service cost and net actuarial loss included in net periodic benefit cost, net of tax amount	(3)	(2)	(5)	(5)
Other comprehensive (loss) gain on unfunded retirement obligations, before tax amount	(5)	(1)	(108)	136
Other comprehensive gain on unfunded retirement obligations, income tax effect	2	1	38	(47)
Other comprehensive gain on unfunded retirement obligations, net of tax amount	(3)	0	(70)	89
Total other comprehensive gain, before tax amount	(5,509)	4,419	(1,961)	9,859
Total other comprehensive gain, income tax effect	1,929	(1,545)	687	(3,450)
Net other comprehensive income (loss)	$ (3,580)	$ 2,874	$ (1,274)	$ 6,409