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Annual retirement benefit paid to terminating eligible directors.

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Service period required to participate in the Defined Contribution Plan.

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Employer contributions to the 401(k) and profit sharing plans funded by the Employee Benefit Trust.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 210
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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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-Name Accounting Standards Codification
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The increase in the fair value of plan assets from contributions made by the employer.

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Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Target allocation of investments of this type to total plan assets presented on a weighted average basis.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

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The amount of the cost recognized during the period for defined contribution plans.

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Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

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Value of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

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Note 12 - Pension and Other Postretirement Benefit Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 1995
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets
Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Benefit Obligation	$ 22,764,000	$ 24,097,000	$ 19,740,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.50%	7.50%	7.50%
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 1,172,000
Postretirement Plans [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Contributions by Employer	63,000	$ 49,000
Defined Benefit Plan, Benefit Obligation	$ 7,977,000	$ 8,073,000	$ 5,586,000
Number of Unfunded Postretirement Benefit Plans	2
Full Time Employment Years of Service	5 years
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 189,000
Postretirement Plan 1 [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Cost Sharing Arrangement, Medical Benefits, Percentage		50.00%
Medical Premiums, Required Percentage to be Paid by Spouses of Future Retirees		100.00%
401(k) [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Contribution Plan Service Period Requirement	1 year
Directors' Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 144,000	$ 120,000
Defined Benefit Plan, Benefit Obligation	$ 2,530,000	2,663,000	2,666,000
Full Time Employment Years of Service	5 years
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 288,000
In Event of Termination [Member] \| Directors' Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Full Time Employment Years of Service	2 years
Defined Benefit Contributions, Months of Benefit Used in Lump Sum Payment	120 months
Trust for Benefit of Employees [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Full Time Employment Years of Service	1 year
Amount Borrowed From the Company by the Employee Benefit Trust				$ 7,900,000
Stock Issued During Period, Value, Employee Benefit Plan				$ 7,000
Stock Issued During Period, Shares, Employee Benefit Plan (in Shares)				2,328,750
Employer Contributions to the 401(k) and Profit Sharing Plans Funded By the Employee Benefit Trust	$ 2,800,000	2,700,000	2,300,000
401(k) [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Vesting Period	5 years
Defined Contribution Plan, Employers Matching Contribution, Vesting Percentage Upon Change of Control	100.00%
Defined Contribution Plan, Cost Recognized	$ 3,000,000	3,100,000	2,900,000
Non-Qualified Deferred Compensation Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Contribution Plan Annual Employer Matching of Employee's Contribution Percent	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	5.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Vesting Period	5 years
Defined Contribution Plan, Employers Matching Contribution, Vesting Percentage Upon Change of Control	100.00%
Defined Contribution Plan, Cost Recognized	$ 400,000	400,000	400,000
Defined Benefit Plan, Assets for Plan Benefits	10,600,000	10,000,000
Savings Bank [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Contributions by Employer	0	0	$ 800,000
Defined Benefit Plan, Benefit Obligation	22,800,000	24,100,000
Savings Bank [Member] \| Directors' Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Benefit Obligation	2,500,000	2,700,000
Defined Benefit Plan, Assets for Plan Benefits	4,200,000	$ 3,900,000
Annual Retirement Benefit Paid to Terminating Eligible Directors	48,000
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	288,000
Savings Bank [Member] \| U.S. Small-Cap Blend [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Pension Plan Assets, Equity Securities Held in Mutual Funds, Minimum Market Capitalization	$ 100,000,000
Savings Bank [Member] \| Equity Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	60.00%
Savings Bank [Member] \| Fixed Income Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	40.00%
Savings Bank [Member] \| 401(k) [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Contribution Plan Annual Employer Matching of Employee's Contribution Percent	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	3.00%
Savings Bank [Member] \| Defined Contribution Retirement Plan ("DCRP") [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	4.00%
Minimum [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Benefit Service Period	3 years
Minimum [Member] \| Savings Bank [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	8.00%
Minimum [Member] \| Savings Bank [Member] \| U.S. Large-Cap Growth [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	55
Minimum [Member] \| Savings Bank [Member] \| U.S. Small-Cap Blend [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	40
Minimum [Member] \| Savings Bank [Member] \| International blend [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	80
Minimum [Member] \| Savings Bank [Member] \| Equity Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	8.00%
Minimum [Member] \| Savings Bank [Member] \| Fixed Income Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	3.00%
Maximum [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Benefit Service Period	10 years
Maximum [Member] \| Savings Bank [Member] \| U.S. Large-Cap Growth [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	70
Maximum [Member] \| Savings Bank [Member] \| U.S. Small-Cap Blend [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	100
Maximum [Member] \| Savings Bank [Member] \| International blend [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Number of Stocks Held in Portfolio	90
Maximum [Member] \| Savings Bank [Member] \| Equity Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	10.00%
Maximum [Member] \| Savings Bank [Member] \| Fixed Income Securities [Member] \| Retirement Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	5.00%
Less Than [Member] \| In Event of Termination [Member] \| Directors' Plan [Member]
Note 12 - Pension and Other Postretirement Benefit Plans (Details) [Line Items]
Full Time Employment Years of Service	2 years