Non-controlling Interest - Distributions Paid or Payable (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 21, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends Payable [Line Items]
Distributions paid or payable to or on behalf of non-controlling unitholders		$ 17,260	$ 17,927
Tax and other distributions
Dividends Payable [Line Items]
Distributions paid or payable to or on behalf of non-controlling unitholders		8,217	10,391
Dividend distributions
Dividends Payable [Line Items]
Distributions paid or payable to or on behalf of non-controlling unitholders		$ 9,043	$ 7,536
Subsequent Event | Quarterly distribution
Dividends Payable [Line Items]
Distributions declared to non-controlling unitholders	$ 2,500