Employee Benefit Plans - Schedule of Categorization of Plans' Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	$ 656,084	$ 672,576
Fair Value of Plan Assets excluding the fair value of plan liabilities	656,668
Plan liabilities measured at Fair Value	584
NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	332,084	366,429
Derivative Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value		304
Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan liabilities measured at Fair Value	584
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	19,172	13,226
Debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	56,247	52,439
Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	25,901	31,253
Alternative Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	1,193	1,035
Alternative Investment Funds [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	525	578
Debt Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	337,011	372,885
Debt Funds [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	325,312	359,315
Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	217,144	201,434
Equity Funds [Member] | NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	6,247	6,536
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	324,584	305,843
Level 1 [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	19,172	13,226
Level 1 [Member] | Debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	56,247	52,439
Level 1 [Member] | Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	25,901	31,253
Level 1 [Member] | Alternative Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	668	457
Level 1 [Member] | Debt Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	11,699	13,570
Level 1 [Member] | Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value	210,897	194,898
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value		304
Plan liabilities measured at Fair Value	584
Level 2 [Member] | Derivative Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets measured at fair value		$ 304
Level 2 [Member] | Derivative [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan liabilities measured at Fair Value	$ 584