Earnings 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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic earnings per share
Net income	$ 143,232	$ 428	$ 170,981	$ 5,563
Weighted-average common shares outstanding (denominator)	36,925	28,916	36,902	28,857
Basic earnings per share	$ 3.82	$ 0.01	$ 4.56	$ 0.19
Diluted earnings per share
Net income	143,232	428	170,981	5,563
Weighted-average common shares outstanding	36,925	28,916	36,902	28,857
Add: effect of dilutive stock options and convertible notes	660	169	711	158
Diluted weighted-average common shares outstanding (denominator)	37,585	29,085	37,613	29,015
Diluted earnings per share	$ 3.75	$ 0.01	$ 4.47	$ 0.19
Basic Earnings Per Share [Member]
Basic earnings per share
Less: net income allocated to unvested participating securities	(2,351)	(11)	(2,831)	(143)
Net income available to common stockholders (numerator)	140,881	417	168,150	5,420
Diluted earnings per share
Less: net income allocated to unvested participating securities	(2,351)	(11)	(2,831)	(143)
Diluted Earnings Per Share [Member]
Basic earnings per share
Less: net income allocated to unvested participating securities	(2,310)	(11)	(2,778)	(142)
Diluted earnings per share
Less: net income allocated to unvested participating securities	(2,310)	(11)	(2,778)	(142)
Net income available to common stockholders (numerator)	$ 140,922	$ 417	$ 168,203	$ 5,421