Employee Benefit Plans - Return on Current and Target Asset Allocation (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 22,015	$ 19,933	$ 19,725
Total fair value of plan assets, not including pooled funds	6,205	14,603
Pooled funds	15,810	5,330
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	366	1,149
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,468	3,986
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,611	9,468
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	760	0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets, not including pooled funds	6,205	14,603
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	366	1,149
Level 1 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,468	3,986
Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,611	9,468
Level 1 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	760	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets, not including pooled funds	0	0
Level 2 | Cash and cash equivalents
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	0	0
Level 2 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets, not including pooled funds	0	0
Level 3 | Cash and cash equivalents
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
Level 3 | Other Investments
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 0	$ 0