Net Income per Share (EPS) (Details) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic shares	50,894	50,820	49,405
Business combination obligations payable in a fixed dollar amount of shares		200	674
Diluted shares	51,572	51,371	50,447
Antidilutive shares	589	843	627
Method of calculating diluted stock	We use the treasury stock method to calculate the dilutive effect of our common stock equivalents should they vest. The exercise of stock options or vesting of restricted stock and restricted stock units triggers excess tax benefits or tax deficiencies that reduce or increase the dilutive effect of such common stock being issued. The excess tax benefits or deficiencies are based on the difference between the market price of our common stock on the date the equity award is exercised or vested and the cumulative compensation cost of the stock options, restricted shares and restricted stock units. These excess tax benefits are recorded as a component of additional paid-in capital in the accompanying consolidated balance sheets and as a component of financing cash flows in the accompanying consolidated statements of cash flows. The excess tax deficiencies are recorded as a component of additional paid-in capital in the accompanying consolidated balance sheets and as a component of operating cash flows in the accompanying consolidated statements of cash flows.
Stock Options [Member]
Share-based Awards	92	87	222
Restricted Stock [Member]
Share-based Awards	562	264	117