Note 12 - Pension and Other Postretirement Benefit Plans (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 1995
U.S. large-cap growth [Member] | Minimum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	55
U.S. large-cap growth [Member] | Maximum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	70
U.S. Small-Cap Blend [Member] | Minimum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	40
U.S. Small-Cap Blend [Member] | Maximum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	100
U.S. Small-Cap Blend [Member] | Retirement Plan [Member] | Savings Bank [Member]
Pension Plan Assets, Equity Securities Held in Mutual Funds, Minimum Market Capitalization	$ 100,000,000
International blend [Member] | Minimum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	80
International blend [Member] | Maximum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Number of Stocks Held in Portfolio	90
Equity Securities [Member] | Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Target Plan Asset Allocations	60.00%
Fixed Income Securities [Member] | Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Target Plan Asset Allocations	40.00%
Trust for Benefit of Employees [Member]
Amount Borrowed From the Company by the Employee Benefit Trust				7,928,000
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	2,100,000	2,000,000	1,600,000
401(k) [Member] | Savings Bank [Member]
Defined Contribution Plan Annual Employer Matching Of Employee's Contribution Percent	50.00%
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	3.00%
401(k) [Member]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Employers Matching Contribution, Vesting Percentage Upon Change of Control	100.00%
Defined Contribution Plan, Cost Recognized	2,400,000	2,300,000	2,200,000
Defined Contribution Retirement Plan ("DCRP") [Member] | Savings Bank [Member]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	4.00%
Non-Qualified Deferred Compensation Plan [Member]
Defined Contribution Plan Annual Employer Matching Of Employee's Contribution Percent	50.00%
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	5.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	20.00%
Defined Contribution Plan, Employers Matching Contribution, Vesting Percentage Upon Change of Control	100.00%
Defined Contribution Plan, Cost Recognized	400,000	300,000	300,000
Minimum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	6.00%
Maximum [Member] | Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	10.00%
Retirement Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Contributions by Employer	700,000	2,700,000
Defined Benefit Plan, Benefit Obligation	22,500,000	21,100,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	831,000
Retirement Plan [Member]
Defined Benefit Plan, Contributions by Employer	723,000	2,734,000
Defined Benefit Plan, Benefit Obligation	22,531,000	21,101,000	17,972,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	7.50%	8.00%	8.50%
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	1,022,000
Postretirement Plan 1 [Member]
Cost Sharing Arrangement, Medical Benefits, Percentage	50.00%
Medical Premiums, Required Percentage to Be Paid By Spouses of Future Retirees	100.00%
Postretirement Plans [Member]
Defined Benefit Plan, Contributions by Employer	67,000	53,000
Defined Benefit Plan, Benefit Obligation	5,927,000	5,166,000	4,013,000
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	161,000
Directors' Plan [Member] | Savings Bank [Member]
Defined Benefit Plan, Benefit Obligation	2,700,000	2,600,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	216,000
Annual Retirement Benefit Paid to Terminating Eligible Directors	48,000
Directors' Plan [Member]
Defined Benefit Plan, Contributions by Employer	87,000	87,000
Defined Benefit Plan, Benefit Obligation	2,706,000	2,647,000	2,473,000
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 216,000