Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Equity:
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, authorized	5,000,000	5,000,000
Preferred stock, issued
Preferred stock, outstanding
Common stock, par value	$ 0.20	$ 0.20
Common stock, authorized	500,000,000	500,000,000
Common stock, shares issued	137,082,096	141,009,834
Common stock, shares outstanding	137,082,096	141,009,834
Treasury stock, at cost	98,035,822	94,108,084