CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	77,178,934	76,713,154
Treasury stock, at cost, shares	25,295,636	25,280,364