Partners' Equity, Cash Distributions (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Allocations of Quarterly Cash Distributions to General and Limited Partners
Partners' Capital, Distribution Amount Per Share	$ 0.5225		$ 0.5225
Partner Distributions
General partner interest	$ 825,000	$ 754,000	$ 2,422,000	$ 2,210,000
Incentive Distribution, Distribution	8,517,000	6,827,000	24,283,000	19,215,000
Total general partner distribution	9,342,000	7,581,000	26,705,000	21,425,000
Limited partner distribution	30,648,000	28,889,000	90,625,000	85,346,000
Total regular quarterly cash distribution	39,990,000	36,470,000	117,330,000	106,771,000
Cash distribution per unit applicable to limited partners	$ 0.5225	$ 0.4925	$ 1.5450	$ 1.455
Excess Acquisition Costs, Not Recognized due to Common Control	$ 305,300,000		$ 305,300,000