Partners' Capital, Mezzanine and Equity Distributions (Distributions Paid) (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 14, 2018	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016	Feb. 12, 2016	Dec. 31, 2017	[1]	Sep. 30, 2017	[1]	Jun. 30, 2017	[1]	Mar. 31, 2017	[1]	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]
Distribution Made to Limited Partner [Line Items]
Date Paid		Nov. 14, 2017	Aug. 14, 2017	May 15, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016	Feb. 12, 2016
Per Unit Amount (in dollars per share)		$ 0.5000	$ 0.7225	$ 0.7200	$ 0.7100	$ 0.7000	$ 0.6900	$ 0.6725	$ 0.6550	$ 0.5000		$ 0.7225		$ 0.7200		$ 0.7100		$ 0.7000		$ 0.6900		$ 0.6725		$ 0.6550
Total Amount		$ 61,290	$ 88,563	$ 88,257	$ 83,765	$ 82,585	$ 81,406	$ 73,961	$ 72,036
Subsequent Event [Member]
Distribution Made to Limited Partner [Line Items]
Date Paid	Feb. 14, 2018
Per Unit Amount (in dollars per share)	$ 0.5100
Total Amount	$ 62,515

[1] (1)Represents cash distributions declared and paid in the applicable period.