Partners' Capital (Class B Preferred Units) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Mezzanine equity beginning balance	$ 343,912
Distributions	17,500	$ 14,000
Total mezzanine equity	346,761		$ 343,912
Class B preferred units
Mezzanine equity beginning balance	343,912	$ 342,991	342,991
Amortization of discount	1,099		1,796
Distributions	19,250		35,875
Distributions paid	(17,500)		(36,750)
Total mezzanine equity	$ 346,761		$ 343,912

Carrying amount, attributable to parent, of an entity's issued and outstanding stock which is not included within permanent equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. Includes stock with a put option held by an ESOP and stock redeemable by a holder only in the event of a change in control of the issuer.

No definition available.

Name:	us-gaap_TemporaryEquityCarryingAmountAttributableToParent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant