Share-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 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	$ 1.3	$ 1.8
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
2011 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)	289,125
Vesting period (in years)	3 years
Granted (in dollars per share)	$ 13.06
2010 Incentive Plan | Stock options
Stock Compensation
Options outstanding (in shares)	200,115