Unit-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended				1 Months Ended
	Mar. 31, 2014	Sep. 30, 2014	Apr. 30, 2014 Service Restricted Units [Member]	Apr. 30, 2013 Service Restricted Units [Member]	Sep. 30, 2014 Service Restricted Units [Member]	Sep. 30, 2013 Service Restricted Units [Member]	Sep. 30, 2014 Service Restricted Units [Member]	Sep. 30, 2013 Service Restricted Units [Member]	Apr. 30, 2014 Performance Restricted Units [Member]	Apr. 30, 2013 Performance Restricted Units [Member]	Sep. 30, 2014 Performance Restricted Units [Member]	Sep. 30, 2013 Performance Restricted Units [Member]	Sep. 30, 2014 Performance Restricted Units [Member]	Sep. 30, 2013 Performance Restricted Units [Member]	Sep. 30, 2014 Minimum [Member] Performance Restricted Units [Member]	Sep. 30, 2014 Maximum [Member] Performance Restricted Units [Member]	Apr. 30, 2014 Independent Directors Of The Partnership [Member]	Apr. 30, 2013 Independent Directors Of The Partnership [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common unit awards authorized		1,800,000
Increase in authorization of additional units under Long Term Incentive Plan	3,000,000
Units granted to employees			550,000	455,000			570,274		135,000	149,000			135,208				20,000	20,000
Compensation expense					$ 2.0	$ 1.7	$ 4.6	$ 4.6			$ 0.4	$ 0.2	$ 1.2	$ 0.5
Final shares to be issued based on initial shares granted, percentage															0.00%	225.00%
Weighted average grant date fair value, granted							$ 18.00						$ 12.33
Performance units earned period													3 years