Long-Term Debt 2018 Private Offering of Senior Notes (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2019
Redemption of preferred units	$ (300)
Common Unit Repurchase, Cash Consideration	540
Four Point Eight Seven Five Percentage Senior Notes Due Two Thousand Twenty Three [Member] \| Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		4.85%
Five Point Five Zero Zero Percentage Senior Notes Due Two Thousand Twenty Six [Member] \| Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		5.50%
Five Point Eight Seven Five Percentage Senior Notes Due Two Thousand Twenty Eight [Member] \| Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage		5.875%
Series A Preferred Units [Member]
Redemption of preferred units	(300)
Common Unit Repurchase, Cash Consideration	$ 0

Contractual interest rate for funds borrowed, under the debt agreement.

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