Supplemental Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total Revenues	$ 190,765	$ 181,674	$ 170,660	$ 160,702	$ 151,150	$ 154,925	$ 139,435	$ 113,225	$ 703,801	$ 558,735	$ 289,622
Operating Income	69,644	81,271	60,564	71,987	63,768	56,779	51,985	46,346	283,466	218,878	184,008
Income Before Income Taxes	52,190	71,698	56,494	69,100	64,971	57,160	54,408	48,181	249,482	224,720	188,739
Net Income	51,394	70,519	55,763	67,791	63,025	55,415	52,097	46,182	245,467	216,719	160,767
Net Income Attributable to Limited Partners	$ 39,396	$ 34,812	$ 31,769	$ 40,052	$ 39,751	$ 43,155	$ 35,450	$ 38,542	146,029	156,898	139,737
Common Units
Net Income Attributable to Limited Partners									123,662	93,875	75,076
Net Income Attributable to Limited Partners Per Limited Partner Unit — Basic and Diluted (in dollars per share)	$ 0.65	$ 0.88	$ 0.79	$ 1.01	$ 1.00	$ 1.09	$ 0.90	$ 0.97
Subordinated Units
Net Income Attributable to Limited Partners									$ 22,367	$ 63,023	$ 64,661
Net Income Attributable to Limited Partners Per Limited Partner Unit — Basic and Diluted (in dollars per share)	$ 0	$ 0	$ 0.84	$ 1.01	$ 1.00	$ 1.09	$ 0.90	$ 0.97