Stock-Based Compensation Plans (Details 4) (Employee Stock Purchase Plan, USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Stock Purchase Plan
Stock-Based Compensation Plans - Disclosures
Maximum value of company common stock that can be purchased by an employee per year	$ 25,000
Employee purchase price as a percent of fair market value (as a percent)	85.00%
Share purchases under employee stock purchase plan (in shares)	0.7	0.9	1.1
Weighted-average fair value of discount on employee stock purchase plan (in dollars per share)	$ 4.20	$ 7.43	$ 5.08
Intrinsic value from shares settled	3,100,000	6,800,000	5,600,000
Cash received from shares issued	18,700,000	18,500,000	13,800,000
Tax benefits realized from the settlement of share-based payment arrangements	$ 700,000	$ 700,000	$ 400,000
Shares available to be issued under employee stock purchase plan (in shares)	6.9