Consolidated Statements of Changes in Equity (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Contingent convertible preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Treasury stock, par value (usd per share)	$ 0.01	$ 0.01
Common Stock
Common stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01
Treasury Stock
Treasury stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01
Contingent Convertible Preferred Stock
Contingent convertible preferred stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01