Accounting for Stock-Based Compensation (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended									3 Months Ended
	Mar. 31, 2012 M	Mar. 31, 2011	Mar. 31, 2012 Contractual Term of Option Granted Prior to 2005 [Member]	Mar. 31, 2012 Contractual Term of Option Granted from 2005 Through 2007 [Member]	Mar. 31, 2012 Contractual term of option granted from 2008 through 2012 [Member]	Mar. 31, 2012 Plan 2000 [Member]	Mar. 31, 2012 Plan 2009 [Member]	Mar. 31, 2012 Employee Stock Option [Member]	Mar. 31, 2012 Restricted Stock Restricted Stock Units and Phantom Shares [Member]	Mar. 31, 2012 Phantom Stock and Restricted Stock Units [Member] M	Feb. 24, 2010 Phantom Stock and Restricted Stock Units [Member] Plan 2000 [Member]	May 19, 2009 Phantom Stock and Restricted Stock Units [Member] Plan 2000 [Member]	Feb. 25, 2009 Phantom Stock and Restricted Stock Units [Member] Plan 2000 [Member]	Feb. 16, 2012 Phantom Stock and Restricted Stock Units [Member] Plan 2009 [Member]	Feb. 23, 2011 Phantom Stock and Restricted Stock Units [Member] Plan 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unissued common stock reserved for grants						446,221	1,529,549
Employee Service Share-based Compensation, Unrecognized Compensation Costs on Nonvested Awards	$ 64.9							$ 13.1	$ 51.8
Weighted Average Period in months	23									24
Closing price of Company's common stock	$ 22.24
Number of shares received by Director.											4,130	7,151	7,151	6,645	3,688
Contractual term of option granted			10 years	8 years	10 years
Accounting For Stock Based Compensation (Textual) [Abstract]
Weighted-average grant date fair value of stock options	$ 9.15	$ 10.34
Aggregate fair value, Deferred in plan	0.7
Aggregate intrinsic value of options exercised	$ 0.1	$ 5.9
Share equivalent units, Deferred in the plan	30,012
Valuation method used to estimate the fair value of stock options	Black Scholes option pricing model