Share-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Assumptions used to determine value of the shares purchased under the stock purchase plan using Black-Scholes option pricing model
Equity-based compensation expense	$ 1.1	$ 1.2	$ 2.4	$ 3.0
Stock options
Assumptions used to determine value of the shares purchased under the stock purchase plan using Black-Scholes option pricing model
Expected annual dividend rate (as a percent)			1.23%
Risk-free interest rate (as a percent)			0.81%
Average expected life (in years)			5.6
Expected volatility of common stock (as a percent)			0.409%
Forfeiture rate (as a percent)			0.00%
Weighted average fair value of option grants (in dollars per share)			$ 4.43
Restricted Stock | Directors
Assumptions used to determine value of the shares purchased under the stock purchase plan using Black-Scholes option pricing model
Granted (in shares)			27,874
2010 Incentive Plan | Stock options
Stock Compensation
Options outstanding (in shares)	200,115		200,115
2010 Incentive Plan | Restricted Stock
Assumptions used to determine value of the shares purchased under the stock purchase plan using Black-Scholes option pricing model
Granted (in shares)			290,265
Vesting period			3 years
Granted (in dollars per share)			$ 13.06