Summary of Non Vested Restricted Stock Unit Activity (Detail) (Restricted Stock Units, USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted Stock Units
Schedule Of Activity Related To Restricted Shares And Restricted Share [Line Items]
Number of Non-Vested Shares, Outstanding, beginning of the year	364,788
Number of Non-Vested Shares, Granted	148,191
Number of Non-Vested Shares, Vested	(99,666)
Number of Non-Vested Shares, Forfeited	(59,956)
Number of Non-Vested Shares, Outstanding, end of the year	353,357	364,788
Weighted Average Grant Date Fair Value, Outstanding, beginning of the year	$ 55.77
Weighted Average Grant Date Fair Value, Granted	$ 75.60	$ 56.95	$ 54.33
Weighted Average Grant Date Fair Value, Vested	$ 63.01
Weighted Average Grant Date Fair Value, Forfeited	$ 59.87
Weighted Average Grant Date Fair Value, Outstanding, end of the year	$ 62.49	$ 55.77
Weighted Average Remaining Contractual Life In Years, Outstanding, end of the year	1 year 3 months 18 days
Aggregate Intrinsic Value, Outstanding, end of the year	$ 33,166