CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Equity:
Common stock, par value per share (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	59,776,000	59,776,000
Treasury stock, shares (in shares)	3,044,000	3,191,000