Basis of Presentation - Summary of Stock Options Outstanding (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Stock Options:
Outstanding at beginning of period, Shares	712,578	335,730
Granted, Shares	43,686	122,357
Exercised, Shares	(20,366)	(22,283)
Outstanding at end of period, Shares	735,898	435,804
Exercisable at end of period, Shares	137,005	197,943
Weighted-average fair value of awards granted, Shares	$ 17.35	$ 10.32
Outstanding at beginning of period, Weighted-Average Exercise Price	$ 47.42	$ 42.14
Granted, Weighted-Average Exercise Price	$ 71.47	$ 47.50
Exercised, Weighted-Average Exercise Price	$ 33.80	$ 31.36
Outstanding at end of period, Weighted-Average Exercise Price	$ 49.23	$ 44.19
Exercisable at end of period, Weighted-Average Exercise Price	$ 47.08	$ 44.52