Share-Based Arrangements Stock Appreciation Rights Activity (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Stock Appreciation Rights Activity [Roll Forward]
Tax benefit from compensation expense	$ 2.4	$ 1.5	$ 1.1
Tax benefit realized from exercise of stock 0ptions	0.8	0.3	(0.1)
Cost not yet recognized	9.1
Cost not yet recognized, period for recognition	3.1
Stock Appreciation Rights (SARs) [Member]
Stock Appreciation Rights Activity [Roll Forward]
Outstanding at December 31, 2010	21,700
Granted	0
Exercised	(21,700)
Forfeited or expired	0
Outstanding at December 31, 2011	0
SARS outstanding at December 31, 2010, Weighted Average Exercise Price	$ 10.66
Granted, Weighted Average Grant Date Fair Value	$ 0.00
Exercised, Weighted Average Exercise Price	$ (10.66)
Forfeited or expired, Weighted Average Exercise Price	$ 0.00
SARS outstanding at December 31, 2011, Weighted Average Exercise Price	$ 0.00
cash paid to settle stock appreciation rights	$ 0.6		$ 0.1