Stock-Based Compensation (Stock Option Plan Activity) (Details) (USD $)	6 Months Ended
	Jun. 30, 2011 Stock Option Shares [Member]	Jun. 30, 2010 Stock Option Shares [Member]	Jun. 30, 2011 Weighted Average Exercise Price [Member]	Dec. 31, 2010 Weighted Average Exercise Price [Member]	Jun. 30, 2010 Weighted Average Exercise Price [Member]	Dec. 31, 2009 Weighted Average Exercise Price [Member]
Outstanding, beginning of period (in shares)	2,843,909	3,131,142
Granted (in shares)	297,000	389,750
Exercised (in shares)	(118,014)	(83,420)
Forfeited or cancelled (in shares)	(18,250)	(88,930)
Expired (in shares)	(256,250)	(125,400)
Outstanding, end of period (in shares)	2,748,395	3,223,142
Outstanding, beginning of period			$ 38.62	$ 39.22	$ 39.31	$ 39.16
Granted			$ 46.47		$ 42.45
Exercised			$ 33.13		$ 34.98
Forfeited or cancelled			$ 37.39		$ 44.10
Expired			$ 57.00		$ 44.91
Outstanding, end of period			$ 38.62	$ 39.22	$ 39.31	$ 39.16