Summary of Significant Accounting Policies - Additional Information 3 (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Jurisdictions shares	Sep. 30, 2014 USD ($)	Dec. 31, 2014 shares
Operations And Summary Of Significant Accounting Policies [Line Items]
Customary rate	35.00%	35.00%	35.00%	35.00%
State jurisdiction currently under review | Jurisdictions			1
Cumulative common stock ownership change over three year period that could limit federal and state net operating loss carry forwards			50.00%
Rights Plan establishment date			Oct. 01, 2015
Long-term debt, including current portion, Carrying Value	$ 1,297,312		$ 1,297,312
Performance multiplier, minimum			0.00%
Performance multiplier, maximum			300.00%
Interest costs, capitalized during period		$ 2,700	$ 900	$ 7,500
Restricted Stock
Operations And Summary Of Significant Accounting Policies [Line Items]
Shares of unvested restricted stock outstanding | shares	1,575,302		1,575,302		1,207,527
Fixed Rate Debt
Operations And Summary Of Significant Accounting Policies [Line Items]
Long-term debt, including current portion, Carrying Value	$ 1,300,000		$ 1,300,000
Level 2 | Fixed Rate Debt
Operations And Summary Of Significant Accounting Policies [Line Items]
Long-term debt, including current portion, Fair Value	$ 645,600		$ 645,600