Long-Term Incentive Plan (Weighted-Average Grant Date Fair Values) (Details) - Management [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Long Term Incentive Plan [Line Items]
Units granted	174,449
Weighted-Average Grant Date Fair Value	$ 87.68
Equity Method [Member] | Performance Shares [Member]
Long Term Incentive Plan [Line Items]
Units granted	148,028	187,371	182,798
Weighted-Average Grant Date Fair Value	$ 88.78	$ 72.77	$ 51.49
Equity Method [Member] | Time-Based Awards [Member]
Long Term Incentive Plan [Line Items]
Units granted	26,421	33,903	22,668
Weighted-Average Grant Date Fair Value	$ 81.51	$ 82.86	$ 53.02
Liability Method [Member] | Performance Shares [Member]
Long Term Incentive Plan [Line Items]
Units granted	0	0	45,700
Weighted-Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 51.49