Stock Compensation Plans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of all stock compensation plans
Intrinsic value of awards exercised during the year	$ 5,085	$ 3,899	$ 4,352
Fair value of awards vested during the year	2,431	3,857	2,760
Grant date fair value of awards granted during the year	$ 4,333	$ 3,368	$ 2,225