Employee Benefit Plans - Stock Options Awarded Under Stock Option Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period (in shares)	0	4,000	10,000
Granted (in shares)		0	0
Cancelled/Forfeited (in shares)		0	0
Exercised (in shares)		4,000	6,000
Outstanding at end of period (in shares)	0	0	4,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 0.00	$ 10.45	$ 9.91
Granted (in dollars per share)		0.00	0.00
Cancelled/Forfeited (in dollars per share)		0.00	0.00
Exercised (in dollars per share)		17.09	9.54
Outstanding at end of period (in dollars per share)		$ 0.00	$ 10.45