Cash Value of Life Insurance - Summary of Activity in Balance of Cash Value of Life Insurance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Policies Employees Company	Dec. 31, 2015 USD ($) Policies Employees Company	Dec. 31, 2014 USD ($)
Increase (Decrease) in Insurance Liabilities [Abstract]
Beginning balance	$ 94,560	$ 92,337
Increase in cash value of life insurance	2,717	2,786	$ 1,953
Death benefit receivable in excess of cash value	238	155
Death benefit receivable	(1,603)	(718)
Ending balance	95,912	94,560	$ 92,337
End of period death benefit	$ 165,669	$ 166,299
Number of policies owned | Policies	185	187
Insurance companies used | Company	14	14
Current and former employees and directors covered | Employees	58	59