Stock Plans - Share Based Compensation Activity (Detail) - Omnibus Incentive 2006 Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Balance, Shares	282,302
Stock options granted	0	0	0
Exercised, Shares	(75,492)
Canceled, Shares	(301)
Outstanding Balance, Shares	206,509	282,302
Exercisable Balance, Shares	157,417
Outstanding Balance, Weighted Average Exercise Price	$ 30.88
Granted, Weighted Average Exercise Price	0
Exercised, Weighted Average Exercise Price	34.48
Canceled, Weighted Average Exercise Price	40.33
Outstanding Balance, Weighted Average Exercise Price	29.55	$ 30.88
Exercisable Balance, Weighted Average Exercise Price	$ 31.15
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested shares balance, Shares	589,863
Granted, Shares	202,175
Vested, Shares	(250,924)
Canceled, Shares	(775)
Nonvested shares balance, Shares	540,339	589,863
Nonvested shares balance, Weighted Average Grant-Date Fair-Value	$ 36.61
Granted, Weighted Average Grant-Date Fair-Value	57.21	$ 41.61	$ 43.56
Vested, Weighted Average Grant-Date Fair-Value	32.90
Canceled, Weighted Average Grant-Date Fair-Value	50.23
Nonvested shares balance, Weighted Average Grant-Date Fair-Value	$ 43.05	$ 36.61