Non-Vested Stock Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Non-Vested Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested Stock Outstanding, Beginning Balance	500,888
Non-vested Stock Granted, Number of Shares	21,202
Non-vested Stock Vested, Number of Shares	(222,783)
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(89,929)
Non-vested Stock Outstanding, Ending Balance	209,378	500,888
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 18.24
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	50.55	$ 28.48	$ 16.38
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	18.00
Non-vested Stock Canceled, Forfeited or Expired, Weighted Average Grant Date Fair Value	17.26
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 22.20	$ 18.24
Non-Vested Stock Units - Service-Based and Performance-Based [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested Stock Outstanding, Beginning Balance	151,063
Non-vested Stock Granted, Number of Shares	182,796
Non-vested Stock Vested, Number of Shares	(44,729)
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(64,273)
Non-vested Stock Outstanding, Ending Balance	224,857	151,063
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 39.44
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	46.29	$ 39.54
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	34.83
Non-vested Stock Canceled, Forfeited or Expired, Weighted Average Grant Date Fair Value	42.41
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 45.08	$ 39.44
Non-Vested Stock Units - Service-Based and Market-Based [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested Stock Outstanding, Beginning Balance	164,534
Non-vested Stock Granted, Number of Shares	93,257
Non-vested Stock Vested, Number of Shares	(248,654)
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(9,137)
Non-vested Stock Outstanding, Ending Balance	0	164,534
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 10.51
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	10.51
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	10.51
Non-vested Stock Canceled, Forfeited or Expired, Weighted Average Grant Date Fair Value	10.51
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 0	$ 10.51
Non Vested Stock Units Service [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested Stock Outstanding, Beginning Balance	183,332
Non-vested Stock Granted, Number of Shares	147,896
Non-vested Stock Vested, Number of Shares	(32,607)
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(49,192)
Non-vested Stock Outstanding, Ending Balance	249,429	183,332
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 37.89
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	45.60	$ 37.98
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	38.81
Non-vested Stock Canceled, Forfeited or Expired, Weighted Average Grant Date Fair Value	39.38
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 42.05	$ 37.89