Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Preferred stock, par value (usd per share)	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (usd per share)	$ 0.06	$ 0.06
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	143,076,357	144,069,563
Common stock, shares outstanding	143,076,357	144,069,563