Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Stockholders' equity:
Common stock, shares authorized	500,000,000	500,000,000	500,000,000
Common stock, par value	$ 1.00	$ 1.00	$ 1.00
Common stock, shares issued	189,369,450	189,369,450	189,369,450
Treasury shares	538,921	538,921	538,921