Description of Business and Basis of Presentation - Impact of New Accounting Pronouncement - Balance Sheet Table (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Assets
Other current assets	[1]	$ 26,119	$ 15,383
Net property, plant and equipment		6,418,634	5,730,891
Other assets		14,057	12,570
Liabilities
Accrued liabilities	[2]	114,504	47,992
Deferred income taxes		10,285	7,409
Other liabilities	[3]	141,957	3,491
Equity and partners' capital
Total equity and partners' capital		3,616,640	$ 3,944,879
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Assets
Other current assets		23,371
Net property, plant and equipment		6,320,225
Other assets		13,894
Liabilities
Accrued liabilities		106,810
Deferred income taxes		10,519
Other liabilities		2,781
Equity and partners' capital
Total equity and partners' capital		3,661,956
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase / (Decrease) [Member]
Assets
Other current assets		2,748
Net property, plant and equipment		98,409
Other assets		163
Liabilities
Accrued liabilities		7,694
Deferred income taxes		(234)
Other liabilities		139,176
Equity and partners' capital
Total equity and partners' capital		$ (45,316)

[1] Other current assets includes affiliate amounts of $1.4 million and zero as of September 30, 2018, and December 31, 2017, respectively.

[2] Accrued liabilities includes affiliate amounts of $2.3 million and $0.2 million as of September 30, 2018, and December 31, 2017, respectively.

[3] Other liabilities includes affiliate amounts of $50.2 million and $0.7 million as of September 30, 2018, and December 31, 2017, respectively.