Related Party Transactions (Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	May 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Mar. 04, 2014
Related Party Transaction [Line Items]
Long-term receivable from related party	$ 1		$ 1
Centennial
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Blue Water Partners
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%
Crowley Ocean Partners
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	50.00%	50.00%		50.00%
Explorer
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	25.00%				25.00%
Illinois Extension Pipeline
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	35.00%
LOCAP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	59.00%
LOOP
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	51.00%
MarkWest Utica EMG
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	56.00%
Ohio Condensate
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	60.00%
Ohio Gathering
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	34.00%
PFJ Southeast
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	29.00%
TAAE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	45.00%
TACE
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	61.00%
TAME
Related Party Transaction [Line Items]
Equity method investments, ownership percentage	67.00%