Incentive and Restricted Stock Plan and Dividend Reinvestment Plan - Summary of Nonstatutory Stock Options Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nonstatutory Stock Option Activity (shares) [Roll Forward]
Outstanding, beginning of year (in shares)	155,500	428,900	675,500
Granted (in shares)	0	0	0
Exercised (in shares)	0	0	0
Forfeited (in shares)	0	(273,400)	(246,600)
Expired (in shares)	(155,500)	0	0
Outstanding, End of year (in shares)	0	155,500	428,900
Exercisable at End of Year (in shares)	0	155,500	428,900
Nonstatutory Stock Options, Outstanding, Weighted Average Exercise Price (dollars per share) [Abstract]
Outstanding at beginning of year (in dollars per share)	$ 37.86	$ 37.36	$ 35.18
Granted (in dollars per share)	0.00	0.00	0.00
Exercised (in dollars per share)	0.00	0.00	0.00
Forfeited (in dollars per share)	0.00	37.08	31.39
Expired (in dollars per share)	37.86	0.00	0.00
Outstanding and End of Year (in dollars per share)	0.00	37.86	37.36
Exercisable at End of Year (in dollars per share)	$ 0.00	$ 37.86	$ 37.36
Outstanding at End of Year (in years)	0 years	1 year	1 year 4 months 24 days
Exercisable at End of Year (in years)	0 years	1 year	1 year 4 months 24 days