Incentive Plan (Summary Of Long-Term Incentive Units) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Weighted-Average Grant Date Fair Value
Award vesting period	4 years
Long-Term Incentive Units
Units
Unvested beginning of period (shares)	276,669
Granted (shares)	15,745
Vested (shares)	(114,870)
Cancelled or expired (shares)	0
Unvested end of period (shares)	177,544
Weighted-Average Grant Date Fair Value
Unvested beginning of period ($ per share)	$ 62.92
Granted ($ per share)	79.47
Vested ($ per share)	60.23
Cancelled or expired ($ per share)	0.00
Unvested end of period ($ per share)	$ 66.12
Award vesting period	4 years
Share/unit compensation expense	$ 1.0	$ 1.3
Capitalized expense related to construction and leasing activities	0.5	$ 0.9
Unearned compensation	$ 9.6		$ 9.9
Unearned compensation, period of recognition (in years)	887 days