Organization and Summary of Significant Accounting Policies - Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income (numerator):
Net income - basic and diluted	$ 220,511	$ 44,096	$ 405,684	$ 69,094	$ (112,064)	$ 439,143	$ 239,194	$ (137,201)	$ 739,385	$ 429,072	$ 168,255
Weighted average shares - basic									181,340	177,590	168,985
Non-vested restricted stock									490	544	546
Stock options									16	96	248
Weighted average shares - diluted									181,846	178,230	169,779
Net income per share:
Basic	$ 1.20	$ 0.24	$ 2.26	$ 0.38	$ (0.62)	$ 2.45	$ 1.33	$ (0.80)	$ 4.08	$ 2.42	$ 1.00
Diluted	$ 1.19	$ 0.24	$ 2.25	$ 0.38	$ (0.62)	$ 2.44	$ 1.33	$ (0.80)	$ 4.07	$ 2.41	$ 0.99