Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 170,290	$ 86,964	$ 439,453	$ 290,278
Less: Net income attributable to participating securities	(587)	(452)	(1,691)	(1,682)
Net income attributable to common shareholders	$ 169,703	$ 86,512	$ 437,762	$ 288,596