Agreement of Limited Partnership (Tables)

12 Months Ended

Dec. 31, 2017

Distributions Made to Members or Limited Partners [Abstract]

Summary of available cash distribution

In the fourth quarter of 2017, we exceeded the cumulative MQD amounts and will distribute Available Cash as summarized in the following table:

	Quarterly Income and Distribution Allocation
	Target Limit (per unit)		Target Increment (per unit)		Distribution Threshold (in millions) (1)		Common Units		Class B Common Units		General Partner (2)		Total
Minimum Quarterly Distributions	$	0.605	$	0.605	$	11.3	98.990	%	0.985	%	0.025	%	100	%
First Target	0.715		0.110		13.4		98.990	%	0.985	%	0.025	%	100	%
Second Target	0.825		0.110		15.4		85.859	%	0.985	%	13.156	%	100	%
Third Target	1.045		0.220		19.5		75.758	%	0.985	%	23.257	%	100	%
Final Target and Beyond	>1.045		—		> 19.5		50.505	%	0.985	%	48.510	%	100	%

Schedule of the quarterly cash distributions paid to the unitholders and the General Partner

The quarterly cash distributions to the unitholders and the General Partner declared to date in 2018 and during 2017 and 2016 are as follows:

Distribution		Common Units				Class B Common Units				General Partner		Total Distributions Declared
Declared in	Related to	Total		Per unit		Total		Per unit		Total
		(in millions, except per unit amounts)
First Quarter 2018	Fourth Quarter 2017	$	37.6	$	2.03	$	0.6	$	3.10	$	20.4	$	58.6
First Quarter 2017	Fourth Quarter 2016	$	22.6	$	1.22	$	0.3	$	1.52	$	5.7	$	28.6
Second Quarter 2017	First Quarter 2017	17.9		0.97		0.2		1.04		1.4		19.5
Third Quarter 2017	Second Quarter 2017	29.6		1.60		0.4		2.26		12.7		42.7
Fourth Quarter 2017	Third Quarter 2017	25.2		1.36		0.3		1.79		8.3		33.8
First Quarter 2016	Fourth Quarter 2015	$	53.3	$	2.88	$	0.9	$	4.78	$	36.0	$	90.2
Second Quarter 2016	First Quarter 2016	28.0		1.51		0.4		2.09		11.1		39.5
Third Quarter 2016	Second Quarter 2016	47.7		2.58		0.7		4.17		30.4		78.8
Fourth Quarter 2016	Third Quarter 2016	32.7		1.77		0.5		2.60		15.8		49.0