Earnings (Loss) Per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share Computations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Basic earnings (loss) per share
Net income (loss)	$ (12,929)	$ 143,232	$ 4,448	$ 170,981
Less: Net income allocated to unvested participating securities	0	(2,351)	(34)	(2,831)
Net income (loss) available to common stockholders (numerator)	(12,929)	140,881	4,414	168,150
Weighted-average common shares outstanding (denominator) (in shares)	37,673	36,925	37,552	36,902
Basic earnings (loss) per share (in usd per share)	$ (0.34)	$ 3.82	$ 0.12	$ 4.56
Diluted earnings (loss) per share
Net income (loss)	(12,929)	143,232	4,448	170,981
Less: Net income allocated to unvested participating securities	0	2,310	33	2,778
Net income (loss) available to common stockholders (numerator)	$ (12,929)	$ 140,922	$ 4,415	$ 168,203
Weighted-average common shares outstanding (in shares)	37,673	36,925	37,552	36,902
Add: Effect of dilutive stock options and convertible notes	0	660	522	711
Diluted weighted-average common shares outstanding (denominator) (in shares)	37,673	37,585	38,074	37,613
Diluted earnings (loss) per share (in usd per share)	$ (0.34)	$ 3.75	$ 0.12	$ 4.47