Basis of Presentation and Significant Accounting Policies - Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income (numerator):
Net income - basic and diluted	$ 533,521	$ 167,498	$ 863,293	$ 631,395
Weighted average shares - basic	368,814	368,139	368,740	368,072
Non-vested restricted stock	1,714	1,622	1,892	1,485
Weighted average shares - diluted	370,528	369,761	370,632	369,557
Net income per share:
Basic (in dollars per share)	$ 1.45	$ 0.45	$ 2.34	$ 1.72
Diluted (in dollars per share)	$ 1.44	$ 0.45	$ 2.33	$ 1.71