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Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2002	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonstatutory stock options, outstanding	155,500	428,900	675,500		757,050
Aggregate intrinsic value of options outstanding	$ 0	$ 0	$ 0
Aggregate intrinsic value of options exercisable	0	0	0
Share-based compensation arrangement by share-based payment award, options, exercises in period	0	0	0
Restricted shares granted		3,247	9,897
Compensation expense	900,000	600,000	900,000
Tax benefit realized on compensation expense	300,000	200,000	300,000
Unrecognized compensation expense to be recognized	$ 1,500,000
Weighted average compensation expense recognize period	1 year 11 months 19 days
Time-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Award vesting after year two, percent	50.00%		50.00%
Restricted Stock Award vesting after year three, percent	50.00%		50.00%
Performance Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
First Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Award vesting after year two, percent		100.00%	100.00%
Senior Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	66,631	3,247	48,008
Outside Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Restricted shares granted	13,824	18,942	19,362
1992 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorized	3,200,000
Stock plan expiration period	10 years
Nonstatutory stock options and restricted stock granted				3,180,822
Stock plan expiration date	Dec. 31, 2012
2003 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorized	1,500,000
Stock plan expiration period	10 years
Nonstatutory stock options and restricted stock granted	155,500
Vesting period	10 years
Restricted shares granted	259,673
2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorized	750,000
Stock plan expiration period	10 years
Restricted shares granted	80,455
2014 LTIP [Member] \| Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted	66,631
2012 LTIP [Member] \| Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted		0	38,111