Non-Vested Stock Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Non-Vested Stock [Member]
Share Based Compensation [Line Items]
Non-vested Stock Outstanding, Beginning Balance	643,353
Non-vested Stok Granted, Number of Shares	499,049
Non-vested Stock Vested, Number of Shares	(296,597)
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(72,314)
Non-vested Stock Outstanding, Ending Balance	773,491	643,353
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 20.76
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	$ 10.91	$ 14.01	$ 27.05
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	$ 24.29
Non-vested Stock Canceld, Forfeited or Expired, Weighted Average Grant Date Fair Value	$ 15.23
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 13.56	$ 20.76
Non-Vested Stock Units - Service-Based and Performance-Based [Member]
Share Based Compensation [Line Items]
Non-vested Stock Granted, Weighted Average Grant Date Fair Value		$ 56.99	$ 27.40
Non-Vested Stock Units - Service-Based and Market-Based [Member]
Share Based Compensation [Line Items]
Non-vested Stock Outstanding, Beginning Balance	0
Non-vested Stok Granted, Number of Shares	417,330
Non-vested Stock Vested, Number of Shares	0
Non-vested Stock Canceled, Forfeited or Expired, Number of Shares	(27,514)
Non-vested Stock Outstanding, Ending Balance	389,816
Non-vested Stock Outstanding, Beginning Balance, Weighted Average Grant Date Fair Value	$ 0
Non-vested Stock Granted, Weighted Average Grant Date Fair Value	$ 10.51
Non-vested Stock Vested, Weighted Average Grant Date Fair Value	$ 0
Non-vested Stock Canceld, Forfeited or Expired, Weighted Average Grant Date Fair Value	$ 10.51
Non-vested Stock Outstanding, Ending Balance, Weighted Average Grant Date Fair Value	$ 10.51