Post-Retirement Benefit Plans Other than Pensions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2011
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Post retirement benefit plans other than pensions, life insurance plan, coverage value maximum	$ 5,000
Deferred compensation plan interest Rate		3.00%	3.00%	6.00%
Deferred compensation	0
Deferred compensation earnings allocated to the deferred compensation	$ 0	$ 5,000	$ 14,000
Post-Retirement Life Benefit Programs [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Post retirement benefit plans other than pensions, supplemental benefits, age	55 years
Post retirement benefit plans other than pensions, supplemental benefits, years of service	20 years
Post-Retirement Supplemental Medicare Benefits Programs [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Post retirement benefit plans other than pensions, supplemental benefits, age	65 years
Post retirement benefit plans other than pensions, supplemental benefits, years of service	20 years
Other Postretirement Benefit Plan [Member]
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]
Accrued post-retirement benefit cost		$ 143,000