Stockholders' Equity Dividends - Summary of Stock Option Activity under Stock Option Plan (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Shares under option:
Outstanding at beginning of year, Amount	23,350	36,062	38,712
Forfeited, Amount	(1,350)	(450)	(200)
Exercised, Amount	(1,625)	(12,262)	(2,450)
Outstanding at end of year, Amount	20,375	23,350	36,062
Exercisable at end of year, Amount	20,375	23,350	36,062
Available to be granted at end of year, Amount	224,884	223,534	223,084
Outstanding at beginning of year, Weighted Average Exercise Price	$ 31.17	$ 28.90	$ 28.36
Forfeited, Weighted Average Exercise Price	$ 26.68	$ 22.50	$ 15.06
Exercised, Weighted Average Exercise Price	$ 26.76	$ 24.82	$ 21.44
Outstanding at end of year, Weighted Average Exercise Price	$ 31.82	$ 31.17	$ 28.90
Exercisable at end of year, Weighted Average Exercise Price	$ 31.82	$ 31.17	$ 28.90