Equity Method Investments (Schedule Of Equity Method Investments) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Jul. 01, 2014	Jan. 01, 2017
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 865		$ 463
Centennial
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%
Equity method investments	36		29
Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	25.00%
Equity method investments	95		0
Illinois Extension Pipeline Company LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	35.00%			35.00%
Equity method investments	120		0
LOCAP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	59.00%
Equity method investments	23		24
LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	51.00%
Equity method investments	230		214
North Dakota Pipeline Class B Units
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	38.00%	[1]
Equity method investments	216	[1]	24
TAAE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	43.00%
Equity method investments	22		29
TACE
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	60.00%
Equity method investments	61		70
TAEI
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	34.00%
Equity method investments	19		23
TAME
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	67.00%
Equity method investments	24	[2]	35
TAME | Direct Ownership Interest
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage	50.00%	[2]
Other equity method investees
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 19		$ 15
North Dakota Pipeline Class A Units | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Equity method investments, ownership percentage					27.00%

[1] We own a 38 percent interest in the Class B units of this entity. Our Class B units will be converted to an approximate 27 percent ownership interest in the Class A units of this entity upon completion of the Sandpiper pipeline construction project, which is expected to be in 2017.

[2] Excludes TAEI’s investment in TAME.