Stock Plans - Share Based Compensation Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Balance, Shares	1,175,646
Stock options granted
Exercised, Shares	(222,185)
Canceled, Shares	(81,412)
Outstanding Balance, Shares	872,049
Exercisable Balance, Shares	664,627
Outstanding Balance, Weighted Average Exercise Price	$ 26.02
Granted, Weighted Average Exercise Price
Exercised, Weighted Average Exercise Price	$ 23.82
Canceled, Weighted Average Exercise Price	$ 32.55
Outstanding Balance, Weighted Average Exercise Price	$ 25.99
Exercisable Balance, Weighted Average Exercise Price	$ 26.70
Equity Incentive Plan Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares balance, Shares	574,933
Granted, Shares	202,528
Vested, Shares	(72,166)
Canceled, Shares	(95,068)
Nonvested shares balance, Shares	610,227	574,933
Nonvested shares balance, Weighted Average Grant-Date Fair-Value	$ 31.49
Granted, Weighted Average Grant-Date Fair-Value	$ 43.56	$ 33.57	$ 33.26
Vested, Weighted Average Grant-Date Fair-Value	$ 24.99
Canceled, Weighted Average Grant-Date Fair-Value	$ 27.72
Nonvested shares balance, Weighted Average Grant-Date Fair-Value	$ 34.20	$ 31.49