Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock-Based Compensation
Stock-based compensation expense	$ 1.3	$ 2.1	$ 2.3	$ 3.2
Employee, Non-Employee Stock Option [Member]
Stock-Based Compensation
Number of Shares Granted	862,745
Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 2.65
Non-Vested Shares [Member]
Stock-Based Compensation
Number of Shares Granted	401,754
Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 8.19
Performance Shares [Member]
Stock-Based Compensation
Number of Shares Granted	285,841
Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 7.17