Restricted Stock Granted to Executives, Board of Directors, and Employees (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted	79,812		141,480	297,874
Average Grant Date Value	$ 14.32		$ 18.31	$ 12.27
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest Schedule Range	1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest Schedule Range	6 years
Executive officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted	40,750	[1]
Average Grant Date Value	$ 14.11
Executive officer | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest Schedule Range	1 year
Executive officer | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest Schedule Range	6 years
Non-employee directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted	39,062
Average Grant Date Value	$ 14.54
Vest Schedule Range	1 year

[1] *All 40,750 shares were cancelled prior to vest.