Employee Benefit Plans (Pension Benefit Plan) - Schedule of Cash Equivalents and Investments Held at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	$ 190,723	$ 201,133
Total	20,045	19,213	$ 20,338
Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	66,412	57,614
Pension Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash and cash equivalents	6	3
Available-for-sale securities	20,039	19,210
Total	20,045	19,213
Pension Benefit Plan [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	12,546	11,633
Pension Benefit Plan [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash and cash equivalents	6	3
Available-for-sale securities	20,039	19,210
Total	20,045	19,213
Pension Benefit Plan [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	12,546	11,633
Pension Benefit Plan [Member] | Government Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	2,037	1,960
Pension Benefit Plan [Member] | Government Bonds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	2,037	1,960
Pension Benefit Plan [Member] | Large Cap Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	4,462	4,604
Pension Benefit Plan [Member] | Large Cap Blend [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	4,462	4,604
Pension Benefit Plan [Member] | Large Cap Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	249	258
Pension Benefit Plan [Member] | Large Cap Value [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	249	258
Pension Benefit Plan [Member] | Balanced Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	745	755
Pension Benefit Plan [Member] | Balanced Fund [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities	$ 745	$ 755