Note 10 - Income Taxes - Income Tax Reconciliation (Details) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Federal statutory rate | 35.00% | 35.00% | 35.00% |
| Changes from statutory rates resulting from: | |||
| Company-owned life insurance | (1.50%) | (1.60%) | (1.90%) |
| Uncertain tax position | (0.30%) | ||
| Other, net | 0.10% | (0.20%) | 0.40% |
| Effective tax rate on pretax income | 27.90% | 26.10% | 27.00% |
| Interest Income [Member] | |||
| Changes from statutory rates resulting from: | |||
| Tax-exempt interest | (4.60%) | (5.80%) | (5.20%) |
| Interest to Carry Tax-exempt Obligations [Member] | |||
| Changes from statutory rates resulting from: | |||
| Nondeductible interest to carry tax-exempt obligations | 0.20% | 0.20% | 0.20% |
| Other Income [Member] | |||
| Changes from statutory rates resulting from: | |||
| Tax-exempt interest | (1.30%) | (1.50%) | (1.20%) |