Incentive Plan (Long-Term Incentive Units) (Narrative) (Details) - Long-Term Incentive Units - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Share/unit compensation expense	$ 1.5	$ 1.5	$ 4.6	$ 5.2
Capitalized expense related to construction and leasing activities	0.0	$ 0.3	1.1	$ 1.1
Unearned compensation	$ 8.7		$ 8.7		$ 9.3
Unearned compensation, period of recognition			851 days