Employee Benefit Plans - Return on Current and Target Asset Allocation (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 19,933	$ 19,725	$ 18,367
Cash and other investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,149	886
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,986	3,896
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	14,798	14,943
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	14,603	14,469
Level 1 | Cash and other investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,149	886
Level 1 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,986	3,896
Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	9,468	9,687
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	5,330	5,256
Level 2 | Cash and other investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 2 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	5,000	5,256
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 3 | Cash and other investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 3 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 0	$ 0