Equity (Details)	Dec. 31, 2013	Dec. 31, 2012
Summary of preferred stock
Preferred stock, shares authorized	8,000,000	8,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Summary of common stock
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	255,973,000	254,237,000
Common stock, shares outstanding	236,332,000	236,582,000
Series A
Summary of preferred stock
Preferred stock, shares authorized	1,750,000	1,750,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Series X Junior Participating
Summary of preferred stock
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Undesignated
Summary of preferred stock
Preferred stock, shares authorized	5,250,000	5,250,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0