Executive Benefit Agreements and Employee Savings Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Executive Benefit Agreements and Employee Savings Plans [Line Items]
Minimum amount of life insurance policies to be kept by the company for 2005 Agreement	$ 2,500,000
Death Benefit 1992 Agreements [Member]
Executive Benefit Agreements and Employee Savings Plans [Line Items]
Number of equal monthly installments to be paid to the beneficiary under Agreements	120
Minimum amount payable in monthly installments when the employee reaches age 65 under 1992 Agreements	16,000
Maximum amount payable in monthly installments when the employee reaches age 65 under 1992 Agreements	18,000
Death Benefit 1981 Agreements [Member]
Executive Benefit Agreements and Employee Savings Plans [Line Items]
Number of equal monthly installments to be paid to the beneficiary under Agreements	120
Total monthly installments under 1981 Agreements	$ 32,000