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Employee Benefits - Pension Plan Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | $ 84,585 | $ 93,486
Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 3,371 | 5,073
Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 27,054 | 26,726
Equity Index Mutual Funds-International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 3,421 | 3,728
Domestic Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 50,739 | 57,085
International Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value |  | 874
Level 1 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 81,214 | 88,413
Level 1 | Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 1 | Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 27,054 | 26,726
Level 1 | Equity Index Mutual Funds-International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 3,421 | 3,728
Level 1 | Domestic Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 50,739 | 57,085
Level 1 | International Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value |  | 874
Level 2 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 3,371 | 5,073
Level 2 | Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 3,371 | 5,073
Level 2 | Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 2 | Equity Index Mutual Funds-International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 2 | Domestic Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 2 | International Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value |  | 0
Level 3 |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 3 | Cash and Cash Equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 3 | Fixed Income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 3 | Equity Index Mutual Funds-International |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | 0 | 0
Level 3 | Domestic Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value | $ 0 | 0
Level 3 | International Individual Equities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pension plan assets measured at fair value |  | $ 0

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