Components of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Earnings Per Share [Abstract]
Net income (loss)		$ 25,900		$ 89,661	$ (111,394)		$ 8,102
Less: Preferred stock dividends	[1]	(5,935)		(7,641)	(18,069)		(11,081)
Less: Induced conversion of preferred stock		0		(888)	0		(4,256)
Net income (loss) attributable to common shareholders, Basic		19,965		81,132	(129,463)		(7,235)
Add: Preferred stock dividends		5,935	[1]	7,641	0	[1]	0
Add: Induced conversion of preferred stock 1		0		888	0		0
Net loss attributable to common shareholders, Diluted		$ 25,900		$ 89,661	$ (129,463)		$ (7,235)
Weighted-average shares – basic		72,651		71,536	72,438		67,909
Effect of dilutive securities	[2]	30,801		32,070	0		0
Weighted-average shares – diluted		103,452		103,606	72,438		67,909
Potentially dilutive securities with the effect of being anti-dilutive excluded from the calculation of diluted earnings per common share					31,100		24,900

[1] Preferred stock dividends and payments to induce the conversion of preferred stock were excluded from the computation of diluted earnings per share for the nine months ended September 30, 2015 and 2014 as the assumed conversion of the outstanding preferred stock would have been anti-dilutive.

[2] For the nine months ended September 30, 2015 and 2014, approximately 31.1 million and 24.9 million, respectively, of potentially dilutive securities, including the Series A Preferred Stock and Series B Preferred Stock, stock options and restricted stock units, had the effect of being anti-dilutive and were excluded from the calculation of diluted earnings per common share.