Shareholders Equity IPO and Secondary-Offering-Related Expenses Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
IPO and Secondary-Offering- Related Expenses [Line Items]
Accelerated share based compensation expense and related employer payroll taxes	$ 0		$ 40.7		$ 0		$ 40.7
Charge for payment of RDU Plan cash retention pool	0		7.5		0		7.5		7.5
Net proceeds used for termination of management services agreement	0		24.4		0		24.4
Other IPO Related Expenses	0.3	[1]	1.5	[1]	1.2	[1]	1.7	[1]
IPO and Secondary-offering related expenses	$ 0.3		$ 74.1		$ 1.2		$ 74.3

[1] Other expenses include secondary-offering expenses of $0.3 million and $1.2 million for the three and nine months ended September 30, 2014, respectively. There were no secondary-offering expenses recognized during the three and nine months ended September 30, 2013.