Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Total revenues	$ 606,816	$ 569,261	$ 578,602	$ 468,039	$ 575,897	$ 680,670	$ 735,904	$ 607,396	$ 2,222,718	$ 2,599,867	$ 3,501,888
Total operating costs and expenses	579,777	555,990	562,005	454,851	561,557	662,246	722,406	597,864	2,152,623	2,544,073	3,466,281
Operating Income (Loss)	27,039	13,271	16,597	13,188	14,340	18,424	13,498	9,532	70,095	55,794	35,607
Net income	20,752	6,858	9,980	5,757	7,971	12,233	7,120	5,382	43,347	32,706	32,908
Earnings Per Share [Abstract]
Net income attributable to limited partners	$ 20,752	$ 14,023	$ 17,874	$ 14,007	$ 14,842	$ 16,493	$ 15,915	$ 15,323	$ 66,656	$ 62,573	$ 52,992
Earnings Per Share, Basic	$ 0.31	$ 0.23	$ 0.33	$ 0.28	$ 0.30	$ 0.35	$ 0.34	$ 0.33
Earnings Per Share, Diluted	0.31	0.23	0.33	0.28	0.30	0.35	0.34	0.33
Earnings Per Share, Basic and Diluted	$ 0.31	$ 0.25	$ 0.36	$ 0.28	$ 0.29	$ 0.35	$ 0.34	$ 0.33
Weighted Average Number of Shares Outstanding, Basic	38,074	30,884	26,409	24,448	24,314	24,017	24,017	23,985
Weighted Average Number of Shares Outstanding, Diluted	38,095	30,901	26,427	24,454	24,321	24,024	24,051	23,996
Weighted Average Number of Shares Outstanding, Basic and Diluted	22,811	22,811	22,811	22,811	22,811	22,811	22,811	22,811
Scenario, Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenues			$ 578,602	$ 468,039	$ 575,897	$ 680,670	$ 735,904	$ 607,396
Total operating costs and expenses			554,111	446,601	554,141	662,246	714,873	589,835
Operating Income (Loss)			24,491	21,438	21,756	18,424	21,031	17,561
Net income			17,874	14,007	15,387	12,233	14,653	13,411
Scenario, Adjustment [Member]
Condensed Financial Statements, Captions [Line Items]
Total revenues			0	0	0	0	0	0
Total operating costs and expenses			7,894	8,250	7,416	0	7,533	8,029
Operating Income (Loss)			(7,894)	(8,250)	(7,416)	0	(7,533)	(8,029)
Net income			$ (7,894)	$ (8,250)	$ (7,416)	$ 0	$ (7,533)	$ (8,029)