Description of Business and Basis of Presentation - Impact of New Accounting Pronouncement - Balance Sheet Table (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Assets
Other current assets	[1]	$ 23,256	$ 15,383
Net property, plant and equipment		6,063,547	5,730,891
Other assets	[2]	14,525	12,570
Liabilities
Accrued liabilities	[3]	79,122	47,992
Deferred income taxes		8,592	7,409
Other liabilities	[4]	128,757	3,491
Equity and partners' capital
Total equity and partners' capital		3,849,095	$ 3,944,879
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Assets
Other current assets		17,418
Net property, plant and equipment		5,977,144
Other assets		14,303
Liabilities
Accrued liabilities		74,414
Deferred income taxes		8,746
Other liabilities		2,553
Equity and partners' capital
Total equity and partners' capital		3,887,390
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase/(Decrease) [Member]
Assets
Other current assets		5,838
Net property, plant and equipment		86,403
Other assets		222
Liabilities
Accrued liabilities		4,708
Deferred income taxes		(154)
Other liabilities		126,204
Equity and partners' capital
Total equity and partners' capital		$ (38,295)

[1] Other current assets includes affiliate amounts of $5.7 million and zero as of March 31, 2018, and December 31, 2017, respectively.

[2] Other assets includes affiliate amounts of $0.2 million and zero as of March 31, 2018, and December 31, 2017, respectively.

[3] Accrued liabilities includes affiliate amounts of $2.1 million and $0.2 million as of March 31, 2018, and December 31, 2017, respectively.

[4] Other liabilities includes affiliate amounts of $42.4 million and $0.7 million as of March 31, 2018, and December 31, 2017, respectively.