Williams Partners Inactive 8-K7 May 15Other EventsFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	12 Months Ended
Document and Entity Information	Dec. 31, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	Williams Partners L.P.
Entity Central Index Key	1483096
Document Type	8-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (USD $)	12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Service revenues	$3,888	$2,914	$2,714
Product sales	3,521	3,921	4,757
Total revenues	7,409	6,835	7,471
Costs and expenses:
Product costs	3,016	3,027	3,501
Operating and maintenance expenses	1,277	1,080	1,019
Depreciation and amortization expenses	1,151	791	734
Selling, general, and administrative expenses	633	519	583
Net insurance recoveries associated with the Geismar Incident	-232	-40	0
Other (income) expense - net	-45	51	24
Total costs and expenses	5,800	5,428	5,861
Operating income	1,609	1,407	1,610
Equity earnings (losses)	228	104	111
Interest incurred	-683	-477	-458
Interest capitalized	121	90	54
Other income (expense) - net	38	25	16
Income before income taxes	1,313	1,149	1,333
Provision (benefit) for income taxes	29	30	42
Net income	1,284	1,119	1,291
Less: Net income attributable to noncontrolling interests	96	3	0
Net income attributable to controlling interests	1,188	1,116	1,291
Allocation of net income for calculation of earnings per common unit:
Net income attributable to controlling interests	1,188	1,116	1,291
Allocation of net income to general partner	756	505	646
Allocation of net income to Class D Units	73	0	0
Allocation of net income to common units	359	611	645
Basic net income per common unit	$0.99	$1.76	$2.30
Diluted net income per common unit	$0.99	$1.76	$2.30
Basic weighted average number of common units outstanding (thousands)	361,968	346,307	280,806
Diluted weighted average number of common units outstanding (thousands)	361,968	346,307	280,806
Cash distributions per common unit	$3.60	$3.48	$3.21
Other Comprehensive Income (Loss):
Net unrealized gain (loss) from derivative instruments	-1	1	30
Reclassifications into earnings of net derivative instruments (gain) loss	0	0	-30
Foreign currency translation adjustments	-89	-56	20
Other comprehensive income (loss)	-90	-55	20
Comprehensive income	1,194	1,064	1,311
Less: Comprehensive income attributable to noncontrolling interests	96	3	0
Comprehensive income attributable to controlling interests	$1,098	$1,061	$1,311

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$171	$110
Trade accounts and notes receivable - net	905	568
Inventories	231	194
Other current assets	198	96
Total current assets	1,505	968
Investments	8,399	2,187
Property, plant, and equipment - net	27,322	17,625
Goodwill	1,120	646
Other intangible assets - net of accumulated amortization	10,451	1,642
Regulatory assets, deferred charges, and other	525	503
Total assets	49,322	23,571
Accounts payable:
Trade	808	889
Affiliate	137	104
Accrued interest	215	115
Asset retirement obligations	40	64
Other accrued liabilities	392	375
Long-term debt due within one year	4	0
Commercial paper	798	225
Total current liabilities	2,394	1,772
Long-term debt	16,326	9,057
Asset retirement obligations	791	497
Deferred income taxes	133	117
Regulatory liabilities, deferred income, and other	993	561
Contingent liabilities and commitments (Note 17)
Partners' equity
Common units (362,556,333 and 361,619,888 units outstanding at December 31, 2014 and 2013, respectively)	10,367	11,596
Class D units (21,574,035 units outstanding at December 31, 2014)	1,011	0
General partner	9,214	-536
Accumulated other comprehensive income (loss)	2	92
Total partners' equity	20,594	11,152
Noncontrolling interests in consolidated subsidiaries	8,091	415
Total equity	28,685	11,567
Total liabilities and equity	$49,322	$23,571

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical)	Dec. 31, 2014	Dec. 31, 2013
Equity:
Limited partners capital account units outstanding	362,556,333	361,619,888
Class D Partners Capital Account Units Outstanding	21,574,035	0

Consolidated_Statement_of_Chan

Consolidated Statement of Changes in Equity (USD $)	Total	Common Units	Class D	General Partner	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
In Millions	Total	Common Units	Class D	General Partner	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Beginning Balance at Dec. 31, 2011	$6,122	$6,810	$0	($815)	$127	$0
Net income	1,291	672	0	619	0	0
Other comprehensive income (loss)	20	0	0	0	20	0
Cash distributions	-1,440	-1,056	0	-384	0	0
Distributions to The Williams Companies, Inc - net	-16	0	0	-16	0	0
Partners' Capital Account, Sale of Units	2,559	2,559	0	0	0	0
Issuances of common units related to acquisitions	1,044	1,044	0	0	0	0
Issuances Of Common Units In Common Control Transactions	7	345	0	-338	0	0
Contributions from general partner	93	0	0	93	0	0
Proceeds from (Payments to) Noncontrolling Interests	14	0	0	0	0	14
Other	-3	-2	0	-1	0	0
Stockholders' Equity, Period Increase (Decrease)	3,569	3,562	0	-27	20	14
Ending Balance at Dec. 31, 2012	9,691	10,372	0	-842	147	14
Net income	1,119	660	0	456	0	3
Other comprehensive income (loss)	-55	0	0	0	-55	0
Cash distributions	-1,846	-1,422	0	-424	0	0
Distributions to The Williams Companies, Inc - net	221	0	0	221	0	0
Partners' Capital Account, Sale of Units	1,962	1,962	0	0	0	0
Contributions from general partner	78	0	0	78	0	0
Proceeds from (Payments to) Noncontrolling Interests	398	0	0	0	0	398
Other	-1	24	0	-25	0	0
Stockholders' Equity, Period Increase (Decrease)	1,876	1,224	0	306	-55	401
Ending Balance at Dec. 31, 2013	11,567	11,596	0	-536	92	415
Net income	1,284	354	62	772	0	96
Other comprehensive income (loss)	-90	0	0	0	-90	0
Cash distributions	-2,448	-1,706	0	-742	0	0
Distributions to The Williams Companies, Inc - net	18,205	0	0	10,703	0	7,502
Partners' Capital Account, Sale of Units	55	55	0	0	0	0
Issuance of Class D units in common control transaction	0	0	1,017	-1,017	0	0
Beneficial conversion feature of Class D units	0	117	-117	0	0	0
Amortization of beneficial conversion feature of Class D units	0	-49	49	0	0	0
Contributions from general partner	13	0	0	13	0	0
Proceeds from (Payments to) Noncontrolling Interests	334	0	0	0	0	334
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	-243	0	0	0	0	-243
Other	8	0	0	21	0	-13
Stockholders' Equity, Period Increase (Decrease)	17,118	-1,229	1,011	9,750	-90	7,676
Ending Balance at Dec. 31, 2014	$28,685	$10,367	$1,011	$9,214	$2	$8,091

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net income	$1,284	$1,119	$1,291
Adjustments to reconcile to net cash provided by operations:
Depreciation and amortization	1,151	791	734
Provision (benefit) for deferred income taxes	25	50	5
Net gain (loss) on disposition of assets	57	6	7
Amortization of stock-based awards	9	0	0
Cash provided (used) by changes in current assets and liabilities:
Accounts and notes receivable	-169	21	32
Inventories	-36	-17	10
Other current assets and deferred charges	-43	25	25
Accounts payable	-42	-32	-81
Accrued liabilities	-233	171	-23
Affiliate accounts receivable and payable - net	9	-1	42
Other, including changes in noncurrent assets and liabilities	333	36	91
Net cash provided by operating activities	2,345	2,169	2,133
FINANCING ACTIVITIES:
Proceeds from (payments of) commercial paper - net	572	224	0
Proceeds from long-term debt	4,386	2,699	2,639
Payments of long-term debt	-1,157	-2,080	-1,440
Proceeds from sales of common units	55	1,962	2,559
General partner contributions	13	53	93
Distributions to limited partners and general partner	-2,448	-1,846	-1,440
Distributions to noncontrolling interests	-243	0	0
Contributions from noncontrolling interests	334	398	13
Contributions from The Williams Companies, Inc. - net	73	221	9
Payments for debt issuance costs	-24	-12	-12
Other - net	24	-24	17
Net cash provided by financing activities	1,585	1,595	2,438
INVESTING ACTIVITIES:
Capital expenditures	-3,692	-3,316	-2,366
Net proceeds from dispositions	34	3	22
Purchases of businesses	0	0	-2,049
Purchase of business from affiliate	0	25	-25
Purchases of and contributions to equity-method investments	-468	-439	-471
Purchase of ARO trust investments	-52	-58	-34
Proceeds from sale of ARO trust investments	39	46	43
Other - net	270	3	53
Net cash used by investing activities	-3,869	-3,736	-4,827
Increase (decrease) in cash and cash equivalents	61	28	-256
Cash and cash equivalents at beginning of year	110	82	338
Cash and cash equivalents at end of year	171	110	82
Increases to property, plant and equipment	-3,571	-3,333	-2,595
Changes in related accounts payable and accrued liabilities	-121	17	229
Capital expenditures	($3,692)	($3,316)	($2,366)

General_Description_of_Busines

General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies [Text Block]	Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies
	General
	Unless the context clearly indicates otherwise, references in this report to “we,” “our,” “us” or like terms refer to Williams Partners L.P. and its subsidiaries. Unless the context clearly indicates otherwise, references to “we,” “our,” and “us” include the operations in which we own interests accounted for as equity-method investments that are not consolidated in our financial statements. When we refer to our equity investees by name, we are referring exclusively to their businesses and operations.
	We are a publicly traded Delaware limited partnership. WPZ GP LLC, a Delaware limited liability company wholly owned by The Williams Companies, Inc. (Williams), serves as our general partner. Williams owns an approximate 58 percent limited partner interest, a 2 percent general partner interest, and incentive distribution rights (IDRs) in us. Our operations are located in the United States and Canada.
	These financial statements were previously presented as supplemental financial statements because post-merger results had not yet been reported (see below for discussion of the merger). In preparing these financial statements, no changes were made to the previously presented supplemental financial statements except to remove the word “supplemental” and to include the matters discussed in Note 19 – Subsequent Events.
	Merger

	Pursuant to an Agreement and Plan of Merger dated as of October 24, 2014, the general partners of Williams Partners L.P. and Access Midstream Partners, L.P. agreed to combine those businesses and their general partners, with Williams Partners L.P. merging with and into Access Midstream Partners, L.P. and the Access Midstream Partners, L.P. general partner being the surviving general partner (the Merger). Following the completion of the Merger on February 2, 2015, as further described below, the surviving Access Midstream Partners, L.P. changed its name to Williams Partners L.P. and the name of its general partner was changed to WPZ GP LLC. For the purpose of these financial statements and notes, Williams Partners L.P. (WPZ) refers to the renamed merged partnership, while Pre-merger Access Midstream Partners, L.P. (Pre-merger ACMP) and Pre-merger Williams Partners L.P. (Pre-merger WPZ) refer to the separate partnerships prior to the consummation of the Merger and subsequent name change.

	In accordance with the terms of the Merger, each Pre-merger ACMP unitholder received 1.06152 Pre-merger ACMP units for each Pre-merger ACMP unit owned immediately prior to the merger. In conjunction with the Merger, each Pre-merger WPZ common unit held by the public was exchanged for 0.86672 common units of Pre-merger ACMP. Each Pre-merger WPZ common unit held by Williams was exchanged for 0.80036 common units of Pre-merger ACMP. Prior to the closing of the merger, the Class D limited partner units of Pre-merger WPZ, all of which were held by Williams, were converted into Pre-merger WPZ common units on a one-for-one basis pursuant to the terms of the partnership agreement of Pre-merger WPZ. All of the general partner interests of Pre-merger WPZ were converted into general partner interests of Pre-merger ACMP such that the general partner interest of Pre-merger ACMP represents 2 percent of the outstanding partnership interest.

	Description of Business
	Our operations are located in North America and are organized into the following reportable segments: Access Midstream, Northeast G&P, Atlantic-Gulf, West, and NGL & Petchem Services.
	Access Midstream provides domestic gathering, treating, and compression services to producers under long-term, fixed-fee contracts. Its primary operating areas are in the Barnett Shale region of north-central Texas, The Eagle Ford Shale region of South Texas, the Haynesville Shale region of northwest Louisiana, the Marcellus Shale region primarily in Pennsylvania and West Virginia, the Niobrara Shale region of eastern Wyoming, the Utica Shale region of eastern Ohio, and the Mid-Continent region which includes the Anadarko, Arkoma, Delaware and Permian Basins. Access Midstream also includes a 49 percent equity-method investment in Utica East Ohio Midstream, LLC (UEOM), a 50 percent equity-method investment interest in the Delaware Basin gas gathering system in the Mid-Continent region, and Appalachia Midstream Services, LLC, which owns an approximate average 45 percent interest in 11 gas gathering systems in the Marcellus Shale (Appalachia Midstream Investments).
	Northeast G&P is comprised of midstream gathering and processing businesses in the Marcellus and Utica shale regions, as well as a 69 percent equity-method investment in Laurel Mountain Midstream, LLC (Laurel Mountain) and a 58 percent equity-method investment in Caiman Energy II, LLC (Caiman II).
	Atlantic-Gulf is comprised of our interstate natural gas pipeline, Transcontinental Gas Pipe Line Company, LLC (Transco), and significant natural gas gathering and processing and crude oil production handling and transportation in the Gulf Coast region, as well as a 50 percent equity-method investment in Gulfstream Natural Gas System, L.L.C. (Gulfstream), a 41 percent interest in Constitution Pipeline Company, LLC (Constitution) (a consolidated entity), and a 60 percent equity-method investment in Discovery Producer Services LLC (Discovery).
	West is comprised of our gathering, processing, and treating operations in New Mexico, Colorado, and Wyoming and our interstate natural gas pipeline, Northwest Pipeline LLC (Northwest Pipeline).
	NGL & Petchem Services is comprised of our 83.3 percent undivided interest in an olefins production facility in Geismar, Louisiana, along with a refinery grade propylene splitter and pipelines in the Gulf Coast region, an oil sands offgas processing plant located near Fort McMurray, Alberta, and a natural gas liquid (NGL)/olefin fractionation facility and butylene/butane splitter facility at Redwater, Alberta. This segment also includes our NGL and natural gas marketing business, storage facilities and an undivided 50 percent interest in an NGL fractionator near Conway, Kansas, and a 50 percent equity-method investment in Overland Pass Pipeline, LLC (OPPL).
	Basis of Presentation

	Prior to the Merger, Williams owned certain limited partnership interests in both Pre-merger WPZ and Pre-merger ACMP, as well as 100 percent of the general partners of both partnerships. Due to the ownership of the general partners, Williams controlled both partnerships. Williams’ control of Pre-merger WPZ began with its inception in 2005, while control of Pre-merger ACMP was achieved upon obtaining an additional 50 percent interest in its general partner effective July 1, 2014. Williams previously acquired 50 percent of the Pre-merger ACMP general partner in a separate transaction in 2012.

	The Merger has been accounted for as a combination between entities under common control, with Pre-merger WPZ representing the predecessor entity. As such, the accompanying financial statements represent a continuation of Pre-merger WPZ, the accounting acquirer, except for certain adjustments to give effect to the exchange ratio applied to Pre-merger WPZ’s historically outstanding units. Because the Merger was between entities under common control, it was treated similar to a pooling of interests whereby the historical results of operations for Pre-merger ACMP were combined with those of Pre-merger WPZ for periods under common control (periods subsequent to July 1, 2014) and the net assets of Pre-merger ACMP are combined at Williams’ historical basis. (See Note 2 – Acquisitions.)

	Previously presented limited partner units of Pre-merger WPZ have been adjusted to reflect the exchange ratios above, which has resulted in a change to historical earnings per unit. Historical earnings of Pre-merger ACMP prior to the Merger have been presented herein as allocated to either the capital account of the general partner for interests owned by Williams or to noncontrolling interests for interests held by the public. Thus, there was no change in the total amount of historical earnings attributable to common unitholders.
	In February 2014, we acquired certain Canadian operations from Williams (Canada Acquisition) for total consideration of $56 million of cash (including a $31 million post-closing adjustment paid in the second quarter), 25,577,521 Class D limited-partner units, and an increase in the capital account of our general partner to allow it to maintain its 2 percent general partner interest. In lieu of cash distributions, the Class D units received quarterly distributions of additional paid-in-kind Class D units. This common control acquisition was treated similar to a pooling of interests whereby the historical results of operations were combined with ours for all periods presented and the acquired assets and liabilities were combined with ours at their historical amounts. These Canadian operations are reported in our NGL & Petchem Services segment.
	In October 2014, a purchase price adjustment was finalized whereby we received $56 million in cash from Williams in the fourth quarter 2014 and Williams waived $2 million in payments on its IDRs with respect to Pre-merger WPZ’s November 2014 distribution.
	The Canadian operations previously participated in Williams’ cash management program under a credit agreement with Williams. Net changes in amounts due to/from Williams prior to the Canada Acquisition, along with the cash consideration paid for the Canada Acquisition, are reflected within Distributions to the Williams Companies, Inc. - net within the Consolidated Statement of Changes in Equity.
	Prior period amounts and disclosures have been recast for this transaction. The effect of recasting our financial statements to account for this transaction increased net income by $49 million and $59 million for the years ended 2013 and 2012, respectively, and also resulted in Foreign currency translation adjustments of $(56) million and $20 million for the years ended 2013 and 2012, respectively, reflected within Other comprehensive income (loss). This acquisition does not impact historical earnings per unit as pre-acquisition earnings were allocated to our general partner.
	In November 2012, we acquired an entity that holds an 83.3 percent undivided interest in an olefins-production facility in Geismar, Louisiana, and associated assets from Williams for total consideration of 42,778,812 of Pre-merger WPZ’s limited partner units, $25 million in cash, and an increase in the capital account of our general partner to allow it to maintain its 2 percent general partner interest (Geismar Acquisition). The acquired entity was an affiliate of Williams at the time of the acquisition; therefore, the acquisition was accounted for as a common control transaction, whereby the acquired assets and liabilities were combined with ours at their historical amounts. This common control acquisition was treated similar to a pooling of interests whereby the historical results of operations were combined with ours for all periods presented. In first-quarter 2013, we received $25 million in cash from Williams and Williams waived $4 million in payments on its IDRs with respect to Pre-merger WPZ’s May 2013 distribution related to a working capital adjustment associated with the acquisition.
	Summary of Significant Accounting Policies
	Principles of consolidation
	The consolidated financial statements include the accounts of all entities that we control and our proportionate interest in the accounts of certain ventures in which we own an undivided interest. Management’s judgment is required to evaluate whether we control an entity. Key areas of that evaluation include:

	•	Determining whether an entity is a variable interest entity (VIE);


	•	Determining whether we are the primary beneficiary of a VIE, including evaluating which activities of the VIE most significantly impact its economic performance and the degree of power that we and our related parties have over those activities through our variable interests;


	•	Identifying events that require reconsideration of whether an entity is a VIE and continuously evaluating whether we are a VIE’s primary beneficiary;


	•	Evaluating whether other owners in entities that are not VIEs are able to effectively participate in significant decisions that would be expected to be made in the ordinary course of business such that we do not have the power to control such entities.
	We apply the equity method of accounting to investments in entities over which we exercise significant influence but do not control.
	Common control transactions
	Entities and assets acquired from Williams and its affiliates are accounted for as common control transactions whereby the net assets acquired are combined with ours at their historical amounts. If any cash consideration transferred in such a transaction exceeds the carrying value of the net assets acquired, the excess is treated as a capital transaction with our general partner, similar to a dividend. If the carrying value of the net assets acquired exceeds any cash consideration transferred and limited partner units are also issued as consideration, then the limited partner units are recorded at an amount equal to the excess of the carrying value of the net assets acquired over any cash consideration transferred. To the extent that such transactions require prior periods to be recast, historical net equity amounts prior to the transaction date are reflected in the account of the general partner or noncontrolling interests, if applicable. Cash consideration up to the carrying value of net assets acquired is presented as an investing activity in our Consolidated Statement of Cash Flows. Cash consideration in excess of the carrying value of net assets acquired is presented as a financing activity in our Consolidated Statement of Cash Flows.
	Equity-method investment basis differences
	Differences between the cost of our equity-method investments and our underlying equity in the net assets of investees are accounted for as if the investees were consolidated subsidiaries. Equity earnings (losses) in the Consolidated Statement of Comprehensive Income includes our allocable share of net income (loss) of investees adjusted for any depreciation and amortization, as applicable, associated with basis differences.
	Use of estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
	Significant estimates and assumptions include:

	•	Impairment assessments of investments, property, plant, and equipment, goodwill and other identifiable intangible assets;

	•	Litigation-related contingencies;

	•	Environmental remediation obligations;

	•	Depreciation and/or amortization of equity-method investment basis differences;

	•	Asset retirement obligations;

	•	Acquisition related purchase price allocations.

These estimates are discussed further throughout these notes.
Regulatory accounting
Transco and Northwest Pipeline are regulated by the Federal Energy Regulatory Commission (FERC). Their rates, which are established by the FERC, are designed to recover the costs of providing the regulated services, and their competitive environment makes it probable that such rates can be charged and collected. Therefore, our management has determined that it is appropriate to account for and report regulatory assets and liabilities related to these operations consistent with the economic effect of the way in which their rates are established. Accounting for these operations that are regulated can differ from the accounting requirements for nonregulated operations. The components of our regulatory assets and liabilities relate to the effects of deferred taxes on equity funds used during construction, asset retirement obligations, fuel cost differentials, levelized incremental depreciation, negative salvage, and postretirement benefits. Our current and noncurrent regulatory asset and liability balances for the years ended December 31, 2014 and 2013 are as follows:


	December 31,

	2014		2013

	(Millions)

Current assets reported within Other current assets	$	81	$	39

Noncurrent assets reported within Regulatory assets, deferred charges, and other	289		315

Total regulated assets	$	370	$	354



Current liabilities reported within Other accrued liabilities	$	11	$	19

Noncurrent liabilities reported within Regulatory liabilities, deferred income, and other	349		289

Total regulated liabilities	$	360	$	308




Cash and cash equivalents
Cash and cash equivalents in the Consolidated Balance Sheet includes amounts primarily invested in funds with high-quality, short-term securities and instruments that are issued or guaranteed by the U.S. government. These have maturity dates of three months or less when acquired.
Accounts receivable
Accounts receivable are carried on a gross basis, with no discounting, less an allowance for doubtful accounts. We estimate the allowance for doubtful accounts based on existing economic conditions, the financial condition of our customers, and the amount and age of past due accounts. We consider receivables past due if full payment is not received by the contractual due date. Interest income related to past due accounts receivable is generally recognized at the time full payment is received or collectability is assured. Past due accounts are generally written off against the allowance for doubtful accounts only after all collection attempts have been exhausted.
Inventory valuation
All Inventories in the Consolidated Balance Sheet are stated at the lower of cost or market. The cost of inventories is primarily determined using the average-cost method.
Property, plant, and equipment
Property, plant, and equipment is recorded at cost. We base the carrying value of these assets on estimates, assumptions, and judgments relative to capitalized costs, useful lives, and salvage values.
As regulated entities, Northwest Pipeline and Transco provide for depreciation using the straight-line method at FERC-prescribed rates. Depreciation for nonregulated entities is provided primarily on the straight-line method over estimated useful lives, except for certain offshore facilities that apply an accelerated depreciation method. (See Note 11 – Property, Plant and Equipment.)
Gains or losses from the ordinary sale or retirement of property, plant, and equipment for regulated pipelines are credited or charged to accumulated depreciation; other gains or losses are recorded in Other (income) expense – net included in Operating income in the Consolidated Statement of Comprehensive Income.
Ordinary maintenance and repair costs are generally expensed as incurred. Costs of major renewals and replacements are capitalized as property, plant, and equipment.
We record a liability and increase the basis in the underlying asset for the present value of each expected future asset retirement obligation (ARO) at the time the liability is initially incurred, typically when the asset is acquired or constructed. As regulated entities, Northwest Pipeline and Transco offset the depreciation of the underlying asset that is attributable to capitalized ARO cost to a regulatory asset. We measure changes in the liability due to passage of time by applying an interest rate to the liability balance. This amount is recognized as an increase in the carrying amount of the liability and as a corresponding accretion expense included in Operating and maintenance expenses in the Consolidated Statement of Comprehensive Income, except for regulated entities, for which the liability is offset by a regulatory asset as management expects to recover amounts in future rates. The regulatory asset is amortized commensurate with the collection of those costs in rates.
Measurements of AROs include, as a component of future expected costs, an estimate of the price that a third party would demand, and could expect to receive, for bearing the uncertainties inherent in the obligations, sometimes referred to as a market-risk premium.

Goodwill
Goodwill in the Consolidated Balance Sheet represents the excess of the consideration, plus the fair value of any noncontrolling interest or any previously held equity interest, over the fair value of the net assets acquired. It is not subject to amortization but is evaluated annually as of October 1 for impairment or more frequently if impairment indicators are present that would indicate it is more likely than not that the fair value of the reporting unit is less than its carrying amount. As part of the evaluation, we compare our estimate of the fair value of the reporting unit with its carrying value, including goodwill. If the carrying value of the reporting unit exceeds its fair value, a computation of the implied fair value of the goodwill is compared with its related carrying value. If the carrying value of the reporting unit goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in the amount of the excess.
Other intangible assets
Our identifiable intangible assets are primarily related to gas gathering, processing, and fractionation contractual customer relationships. Our intangible assets are amortized on a straight-line basis over the period in which these assets contribute to our cash flows. We evaluate these assets for changes in the expected remaining useful lives and would reflect any changes prospectively through amortization over the revised remaining useful life.
Impairment of property, plant, and equipment, other identifiable intangible assets, and investments
We evaluate our property, plant, and equipment and other identifiable intangible assets for impairment when events or changes in circumstances indicate, in our management’s judgment, that the carrying value of such assets may not be recoverable. When an indicator of impairment has occurred, we compare our management’s estimate of undiscounted future cash flows attributable to the assets to the carrying value of the assets to determine whether an impairment has occurred and we may apply a probability-weighted approach to consider the likelihood of different cash flow assumptions and possible outcomes including selling in the near term or holding for the remaining estimated useful life. If an impairment of the carrying value has occurred, we determine the amount of the impairment recognized in the financial statements by estimating the fair value of the assets and recording a loss for the amount that the carrying value exceeds the estimated fair value. This evaluation is performed at the lowest level for which separately identifiable cash flows exist.
For assets identified to be disposed of in the future and considered held for sale, we compare the carrying value to the estimated fair value less the cost to sell to determine if recognition of an impairment is required. Until the assets are disposed of, the estimated fair value, which includes estimated cash flows from operations until the assumed date of sale, is recalculated when related events or circumstances change.
We evaluate our investments for impairment when events or changes in circumstances indicate, in our management’s judgment, that the carrying value of such investments may have experienced an other-than-temporary decline in value. When evidence of loss in value has occurred, we compare our estimate of fair value of the investment to the carrying value of the investment to determine whether an impairment has occurred. If the estimated fair value is less than the carrying value and we consider the decline in value to be other-than-temporary, the excess of the carrying value over the fair value is recognized in the consolidated financial statements as an impairment charge.
Judgments and assumptions are inherent in our management’s estimate of undiscounted future cash flows and an asset’s or investment’s fair value. Additionally, judgment is used to determine the probability of sale with respect to assets considered for disposal.

Contingent liabilities
We record liabilities for estimated loss contingencies, including environmental matters, when we assess that a loss is probable and the amount of the loss can be reasonably estimated. These liabilities are calculated based upon our assumptions and estimates with respect to the likelihood or amount of loss and upon advice of legal counsel, engineers, or other third parties regarding the probable outcomes of the matters. These calculations are made without consideration of any potential recovery from third parties. We recognize insurance recoveries or reimbursements from others when realizable. Revisions to these liabilities are generally reflected in income when new or different facts or information become known or circumstances change that affect the previous assumptions or estimates.
Cash flows from revolving credit facility and commercial paper program
Proceeds and payments related to borrowings under our credit facility are reflected in the financing activities in the Consolidated Statement of Cash Flows on a gross basis. Proceeds and payments related to borrowings under our commercial paper program are reflected in the financing activities in the Consolidated Statement of Cash Flows on a net basis, as the outstanding notes generally have maturity dates less than three months from the date of issuance. (See Note 13 – Debt, Banking Arrangements, and Leases.)
Derivative instruments and hedging activities
We may utilize derivatives to manage a portion of our commodity price risk. These instruments consist primarily of swaps, futures, and forward contracts involving short- and long-term purchases and sales of physical energy commodities. We report the fair value of derivatives, except those for which the normal purchases and normal sales exception has been elected, in Other current assets; Regulatory assets, deferred charges, and other; Other accrued liabilities; or Regulatory liabilities, deferred income, and other in the Consolidated Balance Sheet. We determine the current and noncurrent classification based on the timing of expected future cash flows of individual trades. We report these amounts on a gross basis. Additionally, we report cash collateral receivables and payables with our counterparties on a gross basis. (See Note 16 – Fair Value Measurements, Guarantees, and Concentration of Credit Risk.)
The accounting for the changes in fair value of a commodity derivative can be summarized as follows:


Derivative Treatment		Accounting Method
Normal purchases and normal sales exception		Accrual accounting
Designated in a qualifying hedging relationship		Hedge accounting
All other derivatives		Mark-to-market accounting
We may elect the normal purchases and normal sales exception for certain short- and long-term purchases and sales of physical energy commodities. Under accrual accounting, any change in the fair value of these derivatives is not reflected on the balance sheet after the initial election of the exception.
We may also designate a hedging relationship for certain commodity derivatives. For a derivative to qualify for designation in a hedging relationship, it must meet specific criteria and we must maintain appropriate documentation. We establish hedging relationships pursuant to our risk management policies. We evaluate the hedging relationships at the inception of the hedge and on an ongoing basis to determine whether the hedging relationship is, and is expected to remain, highly effective in achieving offsetting changes in fair value or cash flows attributable to the underlying risk being hedged. We also regularly assess whether the hedged forecasted transaction is probable of occurring. If a derivative ceases to be or is no longer expected to be highly effective, or if we believe the likelihood of occurrence of the hedged forecasted transaction is no longer probable, hedge accounting is discontinued prospectively, and future changes in the fair value of the derivative are recognized currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income.
For commodity derivatives designated as a cash flow hedge, the effective portion of the change in fair value of the derivative is reported in Accumulated other comprehensive income (loss) (AOCI) in the Consolidated Balance Sheet and reclassified into earnings in the period in which the hedged item affects earnings. Any ineffective portion of the derivative’s change in fair value is recognized currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income. Gains or losses deferred in AOCI associated with terminated derivatives, derivatives that cease to be highly effective hedges, derivatives for which the forecasted transaction is reasonably possible but no longer probable of occurring, and cash flow hedges that have been otherwise discontinued remain in AOCI until the hedged item affects earnings. If it becomes probable that the forecasted transaction designated as the hedged item in a cash flow hedge will not occur, any gain or loss deferred in AOCI is recognized in Product sales or Product costs in the Consolidated Statement of Comprehensive Income at that time. The change in likelihood of a forecasted transaction is a judgmental decision that includes qualitative assessments made by management.
For commodity derivatives that are not designated in a hedging relationship, and for which we have not elected the normal purchases and normal sales exception, we report changes in fair value currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income.
Certain gains and losses on derivative instruments included in the Consolidated Statement of Comprehensive Income are netted together to a single net gain or loss, while other gains and losses are reported on a gross basis. Gains and losses recorded on a net basis include unrealized gains and losses on all derivatives that are not designated as hedges and for which we have not elected the normal purchases and normal sales exception.
Realized gains and losses on derivatives that require physical delivery, as well as natural gas derivatives for NGL processing activities and which are not held for trading purposes nor were entered into as a pre-contemplated buy/sell arrangement, are recorded on a gross basis.
Revenues
As a result of the ratemaking process, certain revenues collected by us may be subject to refunds upon the issuance of final orders by the FERC in pending rate proceedings. We record estimates of rate refund liabilities considering our and other third-party regulatory proceedings, advice of counsel and other risks.
Service revenues
Revenues include services pursuant to long-term firm transportation and storage agreements within our interstate natural gas pipeline businesses. These agreements provide for a reservation charge based on the volume of a contracted capacity and a commodity charge based on the volume of gas delivered, both at rates specified in our FERC tariffs. We recognize revenues for reservation charges ratably over the contract period regardless of the volume of natural gas that is transported or stored. Revenues for commodity charges, from both firm and interruptible transportation services, and storage injection and withdrawal services are recognized when natural gas is delivered at the agreed upon delivery point or when natural gas is injected or withdrawn from the storage facility.
Certain revenues from our midstream operations include those derived from natural gas gathering, processing, treating, and compression services and are performed under volumetric-based fee contracts. These revenues are recorded when services have been performed.
Certain of our gas gathering agreements have minimum volume commitments. If a customer under such an agreement fails to meet its minimum volume commitment for a specified period, generally measured on an annual basis, it is obligated to pay a contractually determined fee based upon the shortfall between actual production volumes and the minimum volume commitment for that period. The revenue associated with minimum volume commitments is recognized in the period that the actual shortfall is determined and is no longer subject to future reduction or offset.
Crude oil gathering and transportation revenues and offshore production handling fees are recognized when the services have been performed. Certain offshore production handling contracts contain fixed payment terms that result in the deferral of revenues until such services have been performed or capacity has been provided.

Storage revenues from our midstream operations associated with prepaid contracted storage capacity contracts are recognized on a straight-line basis over the life of the contract as services are provided.
Product sales
In the course of providing transportation services to customers of our interstate natural gas pipeline businesses, we may receive different quantities of gas from shippers than the quantities delivered on behalf of those shippers. The resulting imbalances are primarily settled through the purchase and sale of gas with our customers under terms provided for in our FERC tariffs. Revenue is recognized from the sale of gas upon settlement of the transportation and exchange imbalances.
We market NGLs, crude oil, natural gas, and olefins that we purchase from our producer customers as part of the overall service provided to producers. Revenues from marketing NGLs are recognized when the products have been sold and delivered.
Under our keep-whole and percent-of-liquids processing contracts, we retain the rights to all or a portion of the NGLs extracted from the producers’ natural gas stream and recognize revenues when the extracted NGLs are sold and delivered.
Our domestic olefins business produces olefins from purchased or produced feedstock and we recognize revenues when the olefins are sold and delivered.
Our Canadian business has processing and fractionation operations where we retain certain NGLs and olefins from an upgrader’s offgas stream and we recognize revenues when the fractionated products are sold and delivered.
Interest capitalized
We capitalize interest during construction on major projects with construction periods of at least 3 months and a total project cost in excess of $1 million. Interest is capitalized on borrowed funds and, where regulation by the FERC exists, on internally generated funds. The latter is included in Other income (expense) – net below Operating income in the Consolidated Statement of Comprehensive Income. The rates used by regulated companies are calculated in accordance with FERC rules. Rates used by nonregulated companies are based on our average interest rate on debt.
Income taxes
We generally are not a taxable entity for income tax purposes, with the exception of Texas franchise tax and foreign income taxes associated with our Canadian operations. Other income taxes are generally borne by individual partners. Net income for financial statement purposes may differ significantly from taxable income of unitholders as a result of differences between the tax basis and financial reporting basis of assets and liabilities and the taxable income allocation requirements under our partnership agreement. The aggregated difference in the basis of our net assets for financial and tax reporting purposes cannot be readily determined because information regarding each partner’s tax attributes in us is not available to us.
Foreign deferred income taxes are computed using the liability method and are provided on all temporary differences between the financial basis and the tax basis of the related assets and liabilities. Our management’s judgment and income tax assumptions are used to determine the levels, if any, of valuation allowances associated with deferred tax assets.
Earnings per unit
We use the two-class method to calculate basic and diluted earnings per unit whereby net income, adjusted for items specifically allocated to our general partner, is allocated on a pro-rata basis between unitholders and our general partner. Basic and diluted earnings per unit are based on the average number of common units outstanding. Basic and diluted earnings per unit are equivalent as there are no dilutive securities outstanding.

Pension and other postretirement benefits
We do not have employees. Certain of the costs charged to us by Williams associated with employees who directly support us include costs related to Williams’ pension and other postretirement benefit plans. (See Note 9 – Benefit Plans.) Although the underlying benefit plans of Williams are single-employer plans, we follow multiemployer plan accounting whereby the amount charged to us, and thus paid by us, is based on our share of net periodic benefit cost.
Foreign currency translation
Our foreign subsidiaries use the Canadian dollar as their functional currency. Assets and liabilities of such foreign subsidiaries are translated at the spot rate in effect at the applicable reporting date, and the combined statements of comprehensive income are translated into the U.S. dollar at the average exchange rates in effect during the applicable period. The resulting cumulative translation adjustment is recorded as a separate component of AOCI.
Transactions denominated in currencies other than the functional currency are recorded based on exchange rates at the time such transactions arise. Subsequent changes in exchange rates when the transactions are settled result in transaction gains and losses which are reflected in the Consolidated Statement of Comprehensive Income.
Accumulated Other Comprehensive Income (Loss)
AOCI is substantially comprised of foreign currency translation adjustments. These adjustments did not impact Net income in any of the periods presented.
Accounting standards issued but not yet adopted
In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update 2014-09 establishing Accounting Standards Codification Topic 606, “Revenue from Contracts with Customers” (ASC 606). ASC 606 establishes a comprehensive new revenue recognition model designed to depict the transfer of goods or services to a customer in an amount that reflects the consideration the entity expects to be entitled to receive in exchange for those goods or services and requires significantly enhanced revenue disclosures. The standard is effective for annual reporting periods beginning after December 15, 2016, and interim periods within the reporting period. Accordingly, we will adopt this standard in the first quarter of 2017. ASC 606 allows either full retrospective or modified retrospective transition and early adoption is not permitted. We continue to evaluate both the impact of this new standard on our consolidated financial statements and the transition method we will utilize for adoption.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions [Text Block]	Note 2 – Acquisitions
	ACMP
	As previously discussed in Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies, these financial statements reflect Williams’ basis in Pre-merger ACMP for periods subsequent to Williams’ acquiring control of Pre-merger ACMP on July 1, 2014 (ACMP Acquisition). Williams’ basis in Pre-merger ACMP reflects its business combination accounting, which, among other things, requires identifiable assets acquired and liabilities assumed to be measured at their acquisition-date fair values.
	The valuation techniques used to measure the acquisition-date fair value of Pre-merger ACMP consisted of valuing the limited partner units and general partner interest separately. The limited partner units of Pre-merger ACMP, consisting of common and Class B units, were valued based on Pre-merger ACMP’s closing common unit price at July 1, 2014. The general partner interest, including IDRs, was valued on a noncontrolling basis using an income approach based on a discounted cash flow analysis and a market comparison analysis based on comparable guideline companies and an implied fair value from Williams’ purchase.
	The following table presents the preliminary allocation of the acquisition-date fair value of the major classes of the assets acquired, which are presented in the Access Midstream segment, liabilities assumed, noncontrolling interest, and equity at July 1, 2014. The allocation is considered preliminary because the valuation work has not been completed due to the ongoing review of the valuation results and validation of significant inputs and assumptions. Significant changes since the allocation disclosed in the third quarter reflect an increase in investments and decreases in goodwill, other intangible assets, and property, plant and equipment - net, generally associated with the attribution of fair value between consolidated and non-consolidated operations. The fair value of accounts receivable acquired equals contractual amounts receivable.


		(Millions)
	Accounts receivable	$	168

	Other current assets	63

	Investments	5,872

	Property, plant, and equipment – net	7,015

	Goodwill	474

	Other intangible assets	9,009

	Current liabilities	(408		)
	Debt	(4,052		)
	Other noncurrent liabilities	(9		)
	Noncontrolling interest in ACMP’s subsidiaries	(958		)
	Noncontrolling interest representing Pre-merger ACMP public unitholders	(6,544		)
	Equity	(10,630		)

	The goodwill recognized in the acquisition relates primarily to enhancing and diversifying our basin positions and was allocated to the reporting units representing the northeast, central, and west regions within our Access Midstream segment.

	Other intangible assets recognized in the acquisition are related to contractual customer relationships from gas gathering agreements with our customers. The basis for determining the value of these intangible assets is estimated future net cash flows to be derived from acquired contractual customer relationships discounted using a risk-adjusted discount rate. These intangible assets are being amortized on a straight-line basis over 30 years during which contractual customer relationships are expected to contribute to our cash flows. Approximately 56 percent of the expected future revenues from these contractual customer relationships are impacted by our ability and intent to renew or renegotiate existing customer contracts. We expense costs incurred to renew or extend the terms of our gas gathering, processing, and fractionation contracts with customers. Based on the estimated future revenues during the current contract periods, the weighted-average periods to the next renewal or extension of the existing customer contracts is approximately 17 years.

	The following unaudited pro forma Revenues and Net income attributable to controlling interests for the years ended December 31, 2014 and 2013, are presented as if the ACMP Acquisition had been completed on January 1, 2013. These pro forma amounts are not necessarily indicative of what the actual results would have been if the acquisition had in fact occurred on the date or for the periods indicated, nor do they purport to project Revenues or Net income attributable to controlling interests for any future periods or as of any date. These amounts do not give effect to any potential cost savings, operating synergies, or revenue enhancements to result from the transactions or the potential costs to achieve these cost savings, operating synergies, and revenue enhancements.



			December 31,
			2014				2013
			(Millions)
	Revenues		$	7,953			$	7,881

	Net income attributable to controlling interests		$	1,376			$	1,172


	Significant adjustments to pro forma Net income attributable to controlling interests include additional depreciation and amortization expense associated with reflecting the acquired investments, property, plant, and equipment, and other intangible assets at fair value. The adjustments assume estimated useful lives of 30 years.

	During the year ended December 31, 2014, ACMP contributed Revenues of $781 million and Net income attributable to controlling interests of $165 million.
	Costs incurred by Williams related to this acquisition are $16 million and are reported within our Access Midstream segment and included in Selling, general, and administrative expenses in our Consolidated Statement of Comprehensive Income. Direct transaction costs associated with financing commitments are $9 million and reported within Interest incurred in our Consolidated Statement of Comprehensive Income.
	Laser and Caiman
	On February 17, 2012, we completed the acquisition of 100 percent of the ownership interests in certain entities from Delphi Midstream Partners, LLC, in exchange for $325 million in cash, net of cash acquired in the transaction, and 7,531,381 Pre-merger WPZ common units valued at $441 million (Laser Acquisition). The fair value of the common units issued as part of the consideration paid was determined on the basis of the closing market price of our common units on the acquisition date, adjusted to reflect certain time-based restrictions on resale. The acquired entities primarily own the Laser Gathering System, which is comprised of a natural gas pipeline and associated gathering facilities in the Marcellus Shale in Susquehanna County, Pennsylvania, as well as gathering lines in southern New York.
	On April 27, 2012, we completed the acquisition of 100 percent of the ownership interests in Caiman Eastern Midstream, LLC, from Caiman Energy, LLC in exchange for $1.72 billion in cash and 11,779,296 Pre-merger WPZ common units valued at $603 million (Caiman Acquisition). The fair value of the common units issued as part of the consideration paid was determined on the basis of the closing market price of our common units on the acquisition date, adjusted to reflect certain time-based restrictions on resale. The acquired entity operates a gathering and processing business in northern West Virginia, southwestern Pennsylvania, and eastern Ohio. Acquisition transaction costs of $16 million were incurred during 2012 by Northeast G&P related to the Caiman Acquisition and are reported in Selling, general, and administrative expenses in the Consolidated Statement of Comprehensive Income.
	The following table presents the allocation of the acquisition-date fair value of the major classes of the net assets, which are included in the Northeast G&P segment:


		Laser				Caiman
		(Millions)
	Assets held-for-sale	$	18			$	—

	Other current assets	3				16

	Property, plant, and equipment	158				656

	Intangible assets	318				1,393

	Current liabilities	(21		)		(94		)
Noncurrent liabilities	—				(3		)

Identifiable net assets acquired	476				1,968

Goodwill	290				356

	$	766			$	2,324

Revenues and earnings related to the Laser and Caiman Acquisitions included within the Consolidated Statement of Comprehensive Income in 2012 are not material.

Variable_Interest_Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2014
Variable Interest Entity Disclosures [Abstract]
Variable Interest Entities [Text Block]	Note 3 – Variable Interest Entities

	Consolidated VIEs
	As of December 31, 2014, we consolidate the following VIEs:
	Gulfstar One
	We own a 51 percent interest in Gulfstar One LLC (Gulfstar One), a subsidiary that, due to certain risk-sharing provisions in its customer contracts, is a VIE. We are the primary beneficiary because we have the power to direct the activities that most significantly impact Gulfstar One’s economic performance. We, as construction agent for Gulfstar One, designed, constructed, and installed a proprietary floating-production system, Gulfstar FPS™, and associated pipelines which began providing production handling and gathering services for the Tubular Bells oil and gas discovery in the eastern deepwater Gulf of Mexico in the fourth quarter of 2014. We received certain advance payments from the producer customers. In certain circumstances, the producer customers could be responsible for Gulfstar One’s unrecovered portion of the firm price of building the facilities if the production handling agreement is terminated. Construction of an expansion project is underway that will provide production handling and gathering services for the Gunflint oil and gas discovery in the eastern deepwater Gulf of Mexico. The expansion project is expected to be in service in the first quarter of 2016. The current estimate of the total remaining construction costs for the expansion project is approximately $150 million, which we expect will be funded with revenues received from customers and capital contributions from us and the other equity partner on a proportional basis.
	Constitution
	We own a 41 percent interest in Constitution, a subsidiary that, due to shipper fixed-payment commitments under its long-term firm transportation contracts, is a VIE. We are the primary beneficiary because we have the power to direct the activities that most significantly impact Constitution’s economic performance. We, as construction agent for Constitution, are building a pipeline connecting our gathering system in Susquehanna County, Pennsylvania, to the Iroquois Gas Transmission and the Tennessee Gas Pipeline systems. We plan to place the project in service in the second half of 2016 and estimate the total remaining construction costs of the project to be approximately $628 million, which will be funded with capital contributions from us and the other equity partners, proportional to ownership interest.
	Cardinal
	We own a 66 percent interest in Cardinal Gas Services, L.L.C (Cardinal Venture), a subsidiary that, due to certain risks shared with customers, is a VIE. We are the primary beneficiary because we have the power to direct the activities that most significantly impact Cardinal Venture’s economic performance. We, as operator for Cardinal Venture, designed, constructed, and installed associated pipelines which will initially provide production handling and gathering services for the Utica region. We received certain advance payments from the equity partners during the construction process.
	Jackalope
	We own a 50 percent interest in Jackalope Gas Gathering Services, L.L.C (Jackalope Venture), a subsidiary that, due to certain risks shared with customers, is a VIE. We are the primary beneficiary because we have the power to direct the activities that most significantly impact Jackalope Venture’s economic performance. We, as operator for Jackalope Venture, designed, constructed, and installed associated pipelines which will initially provide production handling and gathering services for the Niobrara region. We received certain advance payments from the equity partners during the construction process.
	The following table presents amounts included in our Consolidated Balance Sheet that are for the use or obligation of our consolidated VIEs.


		December 31,
		2014			2013			Classification
		(Millions)
	Assets (liabilities):
	Cash and cash equivalents	$	113		$	84		Cash and cash equivalents

	Accounts receivable	52			—			Trade accounts and notes receivable, net

	Other current assets	3			—			Other current assets

	Property, plant, and equipment - net	2,794			1,001			Property, plant, and equipment – net

	Goodwill	103			—			Goodwill

	Other intangible assets, net	1,493			—			Other intangible assets – net of accumulated amortization

	Other noncurrent assets	14			—			Regulatory assets, deferred charges, and other

	Accounts payable	(48		)	(122		)	Accounts payable - trade
	Accrued liabilities	(36		)	(3		)	Other accrued liabilities
	Current deferred revenue	(45		)	(10		)	Other accrued liabilities
	Noncurrent deferred income taxes	(13		)	—			Deferred income taxes

	Asset retirement obligation	(94		)	—			Asset retirement obligations, noncurrent

	Noncurrent deferred revenue associated with customer advance payments	(395		)	(115		)	Regulatory liabilities, deferred income and other
	Nonconsolidated VIEs
	Laurel Mountain
	In October 2014, Laurel Mountain, a previously reported VIE, was restructured removing the customer risk sharing provisions and is no longer considered a VIE as of December 31, 2014. Laurel Mountain continues to be reported as a 69 percent-owned equity-method investment due to the significant participatory rights of our partners such that we do not have control of Laurel Mountain.
	Caiman II
	During April 2014, Caiman II, a previously reported VIE, became able to finance its current activities without additional subordinated financial support due in part to its primary investee, Blue Racer Midstream LLC, securing a revolving credit agreement with a third party. As a result of obtaining the additional financial support, Caiman II is no longer considered a VIE in 2014 but continues to be reported as a 58 percent-owned equity-method investment due to the significant participatory rights of our partners such that we do not have control of Caiman II.

Allocation_of_Net_Income_and_D

Allocation of Net Income and Distributions	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Allocation of Net Income and Distributions	Note 4 – Allocation of Net Income and Distributions
	The allocation of net income among our general partner, limited partners, and noncontrolling interests as reflected in the Consolidated Statement of Changes in Equity is as follows:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Allocation of net income to general partner:
	Net income	$	1,284		$	1,119		$	1,291

	Net income applicable to pre-merger operations allocated to general partner	(95		)	—			—

	Net income applicable to pre-partnership operations allocated to general partner	(15		)	(49		)	(244		)
	Net income applicable to noncontrolling interests	(96		)	(3		)	—

	Costs charged directly to general partner	1			1			1

	Income subject to 2% allocation of general partner interest	1,079			1,068			1,048

	General partner’s share of net income	2		%	2		%	2		%
	General partner’s allocated share of net income before items directly allocable to general partner interest	22			21			21

	Priority allocations, including incentive distributions, paid to general partner	641			387			355

	Costs charged directly to general partner	(1		)	(1		)	(1		)
	Pre-merger net income allocated to general partner interest	95			—			—

	Pre-partnership net income allocated to general partner interest	15			49			244

	Net income allocated to general partner	$	772		$	456		$	619

	Net income	$	1,284		$	1,119		$	1,291

	Net income allocated to general partner’s equity	772			456			619

	Net income allocated to Class D limited partners’ equity (1)	62			—			—

	Net income allocated to noncontrolling interests	96			3			—

	Net income allocated to common limited partners’ equity	$	354		$	660		$	672


	Adjustments to reconcile Net income allocated to common limited partners' equity
	to Allocation of net income to common units:
	Incentive distributions paid	640			383			355

	Incentive distributions declared (2)	(626		)	(432		)	(382		)
	Impact of Class D issuance timing	(9		)	—			—

	Allocation of net income to common units	$	359		$	611		$	645


	____________

	-1	The net income allocated to Pre-merger WPZ Class D limited partners includes $49 million for the year ended December 31, 2014, related to the amortization of the beneficial conversion feature associated with the Pre-merger WPZ Class D units.

	-2	Following the completion of the Merger, we paid a cash distribution of $0.85 per unit on February 13, 2015, on our outstanding common units to unitholders of record at the close of business on February 9, 2015. For the purpose of determining the Allocation of net income to common units for the calculation of earnings per unit, the incentive distribution declared for the fourth quarter of 2014 reflects only the portion of the total incentive distribution associated with the Pre-merger WPZ common units exchanged in the Merger.
	Class D Units
	As previously mentioned (see Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies), a portion of the total consideration for the Canada Acquisition was funded through the issuance of Pre-merger WPZ Class D units to an affiliate of our general partner. The Pre-merger WPZ Class D units were issued at a discount to the market price of Pre-merger WPZ’s common units. The discount represented a beneficial conversion feature and is reflected as an increase in the common unit capital account and a decrease in the Class D capital account on the Consolidated Statement of Changes in Equity. This discount was being amortized through the originally expected first quarter 2016 conversion date, resulting in an increase to the Class D capital account and a decrease to the common unit capital account. The remaining unamortized balance as of December 31, 2014, will be recognized in the first quarter of 2015 due to the Merger. All Pre-merger WPZ Class D units were converted into common units in conjunction with the Merger.
	Distributions
	The Pre-merger WPZ Class D units were not entitled to cash distributions. Instead, prior to conversion into Pre-merger WPZ common units, the Pre-merger WPZ Class D units received quarterly distributions of additional paid-in-kind Pre-merger WPZ Class D units. During 2014, we issued 1,377,893 Pre-merger WPZ Class D units as the paid-in-kind Class D distributions.
	Earnings per unit
	Basic and diluted earnings per limited partner unit are calculated using the two-class method. At December 31, 2014, the Pre-merger WPZ Class D units are anti-dilutive and therefore not included in calculating diluted earnings per common unit.

Related_Party_Transactions

Related Party Transactions

12 Months Ended

Dec. 31, 2014

Related Party Transactions [Abstract]

Related Party Transactions Disclosure [Text Block]

Note 5 – Related Party Transactions

Reimbursement of Expenses of Our General Partner

The employees of Pre-merger WPZ operated assets are employees of Williams. Williams directly charges us for the payroll and benefit costs associated with operations employees and carries the obligations for many employee-related benefits in its financial statements, including the liabilities related to employee retirement, medical plans, and paid time off. Our share of the costs is charged to us through affiliate billings and reflected in Operating and maintenance expenses in the Consolidated Statement of Comprehensive Income.

In addition, employees of Williams provide general and administrative services to us, and we are charged for certain administrative expenses incurred by Williams. These charges are either directly identifiable or allocated to our assets. Direct charges are for goods and services provided by Williams at our request. Allocated charges are based on a three-factor formula, which considers revenues; property, plant, and equipment; and payroll. Our share of direct and allocated administrative expenses is reflected in Selling, general, and administrative expenses in the Consolidated Statement of Comprehensive Income. In management’s estimation, the allocation methodologies used are reasonable and result in a reasonable allocation to us of our costs of doing business incurred by Williams.

The employees of Pre-merger ACMP operated assets were employees of Pre-merger ACMP’s general partner. Pre-merger ACMP’s general partner directly charged Pre-merger ACMP for payroll and benefit costs associated with operations employees and carried the obligations for many employee-related benefits. In addition, Pre-merger ACMP’s general partner charged Pre-merger ACMP for employee related costs for employees who provided general and administrative services to Pre-merger ACMP. These costs are reflected in Operating and maintenance expenses and Selling, general, and administrative expenses in the Consolidated Statement of Comprehensive Income. The employees for Pre-merger ACMP’s general partner became Williams’ employees on January 1, 2015.

In 2012, Williams engaged a consulting firm to assist in better aligning resources to support its business strategy following the December 31, 2011, spin-off of WPX Energy, Inc. (WPX). Our share of the allocated reorganization-related costs, included in Selling, general, and administrative expenses in the Consolidated Statement of Comprehensive Income, is $2 million and $26 million for the years ended December 31, 2013 and 2012, respectively.

Transactions with Equity-Method Investees

Service revenues, in the Consolidated Statement of Comprehensive Income, includes fees received from Appalachia Midstream Investments for the use of compression equipment during the year.

Product costs, in the Consolidated Statement of Comprehensive Income, include charges for the following types of transactions with equity-method investees:

•

Purchases of NGLs for resale from Discovery at market prices at the time of purchase.

•

Payments to OPPL for transportation of NGLs from certain natural gas processing plants.

Summary of the related party transactions discussed in all sections above.

Years Ended December 31,

2014

2013

2012

(Millions)

Service revenues

—

Product costs

186

147

171

Operating and maintenance expenses - employee costs

413

339

275

Selling, general, and administrative expenses:

Employee direct costs

331

270

308

Employee allocated costs

171

169

190

The Accounts payable — affiliate in the Consolidated Balance Sheet represents the payable positions that result from the transactions with affiliates discussed above. We also have $13 million and $13 million in Accounts payable — trade in the Consolidated Balance Sheet with our equity-method investees at December 31, 2014 and 2013, respectively.

Operating Agreements with Equity-Method Investees

We have operating agreements with certain equity-method investees. These operating agreements typically provide for reimbursement or payment to us for certain direct operational payroll and employee benefit costs, materials, supplies, and other charges and also for management services. Williams supplied a portion of these services, primarily those related to employees since we do not have any employees, to certain equity-method investees. The total gross charges to equity-method investees for these fees included in the Consolidated Statement of Comprehensive Income are $75 million, $67 million, and $75 million for the years ended December 31, 2014, 2013, and 2012, respectively.

Omnibus Agreement

In February 2010, Pre-merger WPZ entered into an omnibus agreement with Williams. The terms of this agreement survived the Merger. Under this agreement, Williams is obligated to reimburse us for certain items including (i) maintenance capital expenditure amounts incurred by us or our subsidiaries for certain U.S. Department of Transportation projects, up to a maximum of $50 million, and (ii) an amount based on the amortization over time of deferred revenue amounts that relate to cash payments received by Williams prior to the closing of the contribution transaction for services to be rendered by us in the future at the Devils Tower floating production platform. Net amounts received under this agreement for the years ended December 31, 2014, 2013 and 2012 were $11 million, $12 million, and $15 million, respectively.

We have a contribution receivable from our general partner of $3 million at December 31, 2013, for amounts reimbursable to us under omnibus agreements. We net this receivable against Total partners’ equity in the Consolidated Balance Sheet.

Acquisitions and Equity Issuances

Basis of Presentation in Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies includes related party transactions for the Merger, Geismar, and Canada Acquisitions. Prior to the acquisition, Geismar operations were included in Williams’ cash management program under an unsecured promissory note agreement with Williams for both advances to and from Williams. In connection with the Geismar Acquisition, the outstanding advances were distributed to Williams at the close of the transaction. The distribution had no impact on our assets or liabilities. Changes in the advances to Williams are presented as Distributions to The Williams Companies, Inc.- net in the Consolidated Statement of Changes in Equity. The Canadian operations previously participated in Williams’ cash management program under a credit agreement with Williams. Net changes in amounts due to/from Williams prior to the Canada Acquisition are reflected within Distributions to/Contributions from The Williams Companies, Inc. - net within the Consolidated Statement of Changes in Equity.

Note 14 – Partners’ Capital includes related party transactions for the sale of limited partner units to Williams in March 2013.

Board of Directors

A member of Williams’ Board of Directors, who was elected in 2013, is also the current chairman, president, and chief executive officer of an energy services company that is a customer of ours. We recorded $115 million and $131 million in Service revenues in Consolidated Statement of Comprehensive Income from this company for transportation and storage of natural gas for the years ended December 31, 2014 and December 31, 2013, respectively. This board member does not have any material interest in any transactions between the energy services company and us and he had no role in any such transactions.

Mr. H. Michael Krimbill, a member of our Board of Directors until his term completion in August 2012, has served as the Chief Executive Officer of NGL Energy Partners LP, formerly Silverthorne Energy Partners LP, and as a director of its general partner since 2010. We recorded $61 million in Product sales in the Consolidated Statement of Comprehensive Income from NGL Energy Partners LP primarily for the sale of propane at market prices and $13 million in Product costs in the Consolidated Statement of Comprehensive Income for the purchase of propane at market prices for the year ended December 31, 2012.

Investments

Investments	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Investments [Text Block]	Note 6 – Investments
	Investments accounted for using the equity method consist of:


		December 31,
		2014			2013
		(Millions)
	Appalachia Midstream Investments (2)	$	3,033		$	—

	Delaware Basin gas gathering system – 50% (2)	1,478			—

	UEOM – 49% (2)	1,411			—

	Discovery – 60% (1)	602			527

	Laurel Mountain – 69% (1)	459			481

	OPPL – 50%	453			452

	Caiman II – 58% (1)	432			256

	Gulfstream – 50%	317			333

	Other	214			138

		$	8,399		$	2,187

	____________

	-1	We account for these investments under the equity method due to the significant participatory rights of our partners such that we do not control or are otherwise not the primary beneficiary of the investments.

	-2	These are Pre-merger ACMP investments. The Appalachia Midstream Investments include investments in 11 different gathering systems in the Marcellus Shale. Ownership interests range from 33.75 percent to 67.50 percent, resulting in an overall approximate average interest of 45 percent. For those investments where we own in excess of 50 percent, we apply the equity-method of accounting due to the significant participation rights of our partners such that we do not control. (See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.)
	We have differences between the carrying value of our equity-method investments and the underlying equity in the net assets of the investees of $3.7 billion at December 31, 2014. This difference primarily relates to our investments in Appalachian Midstream Investments, Delaware Basin gas gathering system, and UEOM resulting from property, plant, and equipment, as well as customer-based intangible assets and goodwill. (See Note 2 – Acquisitions.)

	Equity earnings (losses) in 2014 includes $146 million of equity earnings for the last six months of the year from equity-method investments of Pre-merger ACMP, partially offset by $49 million of noncash amortization of the difference between the cost of our investment and our underlying share of the net assets (See Note 2 - Acquisitions).
	We generally fund our portion of significant expansion or development projects of these investees through additional capital contributions. As of December 31, 2014, our proportionate share of amounts remaining to be spent for specific capital projects already in progress for Discovery and Laurel Mountain totaled $98 million and $92 million, respectively. See the table below for significant contributions.


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Caiman II	$	175		$	192		$	69

	Discovery	106			193			169

	Appalachia Midstream Investments	84			—			—

	UEOM	57			—			—

	Delaware Basin gas gathering system	20			—			—

	Laurel Mountain	12			42			174

	The organizational documents of entities in which we have an equity-method interest generally require distribution of available cash to members on a quarterly basis. Dividends and distributions, including those presented below, received from companies accounted for by the equity method of accounting were $344 million, $154 million, and $172 million in 2014, 2013, and 2012, respectively. These transactions reduced the carrying value of our investments. These dividends and distributions primarily included:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Appalachia Midstream Investments	$	120		$	—		$	—

	Gulfstream	81			81			78

	Laurel Mountain	39			—			—

Discovery	36			12			21

OPPL	27			27			28

Aux Sable Liquid Products L.P.	15			20			28


Summarized Financial Position and Results of Operations of All Equity-Method Investments


	December 31,
	2014			2013
	(Millions)
Assets (liabilities):
Current assets	$	599		$	412

Noncurrent assets	9,135			5,956

Current liabilities	(850		)	(264		)
Noncurrent liabilities	(954		)	(1,305		)



	Years Ended December 31,
	2014			2013			2012
	(Millions)
Gross revenue	$	1,623		$	1,333		$	1,213

Operating income	534			367			378

Net income	460			291			309

Other_Income_and_Expenses

Other Income and Expenses	12 Months Ended
	Dec. 31, 2014
Other Income and Expenses [Abstract]
Other Income and Expense [Text Block]	Note 7 – Other Income and Expenses
	The following table presents certain gains or losses reflected in Other (income) expense – net within Costs and expenses in our Consolidated Statement of Comprehensive Income:


			Years Ended December 31,
			2014			2013			2012
			(Millions)
	Access Midstream
	Loss related to sale of certain assets		$	10		$	—		$	—

	Impairment of certain materials and equipment held for sale (See Note 16)		12			—			—

	Northeast G&P
	Contingency gain settlement		(154		)	—			—

	Impairment of certain materials and equipment (See Note 16)		30			—			—

	Net gain related to partial acreage dedication release		(12		)	—			—

	Loss associated with a producer claim		—			25			—

	Atlantic-Gulf
	Amortization of regulatory assets associated with asset retirement obligations		33			30			7

	Impairment of certain equipment		10			—			—

	Write-off of the Eminence abandonment regulatory asset not recoverable through rates		(3		)	12			—

	Insurance recoveries associated with the Eminence abandonment		—			(16		)	—

	Project feasibility costs		2			4			21

	Capitalization of project feasibility costs previously expensed		(5		)	(1		)	(19		)

	The reversals of project feasibility costs from expense to capital are associated with natural gas pipeline expansion projects. These reversals were made upon determining that the related projects were probable of development. These costs are now included in the capital costs of the projects, which we believe are probable of recovery through the project rates.

	In November 2014, we settled a claim arising from the resolution of a contingent gain related to claims associated with the purchase of a business in a prior period. Pursuant to the settlement, we received $154 million in cash, all of which has been recognized as a gain in the fourth quarter of 2014.
	Geismar Incident
	On June 13, 2013, an explosion and fire occurred at our Geismar olefins plant. The incident (Geismar Incident) rendered the facility temporarily inoperable and resulted in significant human, financial, and operational effects.
	At the time of the incident, we had insurance coverage for repair and replacement costs, lost production, and additional expenses related to the incident as follows:

	•	Property damage and business interruption coverage with a combined per-occurrence limit of $500 million and retentions (deductibles) of $10 million per occurrence for property damage and a waiting period of 60 days per occurrence for business interruption;

	•	General liability coverage with per-occurrence and aggregate annual limits of $610 million and retentions (deductibles) of $2 million per occurrence;

	•	Workers’ compensation coverage with statutory limits and retentions (deductibles) of $1 million total per occurrence.
	We expensed $13 million at NGL & Petchem Services during 2013 of costs under our insurance deductibles reported in Operating and maintenance expenses in the Consolidated Statement of Comprehensive Income. During the years ended December 31, 2014 and 2013, we received $246 million and $50 million, respectively, of insurance recoveries related to the Geismar Incident. These amounts are reported within our NGL & Petchem Services segment and reflected as gains in Net insurance recoveries – Geismar Incident in our Consolidated Statement of Comprehensive Income. Also, during the years ended December 31, 2014 and 2013, we incurred $14 million and $10 million, respectively, of covered insurable expenses in excess of our retentions (deductibles) also included in Net insurance recoveries – Geismar Incident.
	Additional Items
	Selling, general, and administrative expenses in 2014 includes $15 million of employee-related transition costs and $11 million of consulting, legal, and accounting fees associated with the Merger reported primarily within the Access Midstream segment. Operating and maintenance expenses in 2014 also includes $15 million of employee-related transition costs associated with the Merger reported within the Access Midstream segment.
	Other income (expense) – net below Operating income includes $34 million, $20 million, and $15 million for allowance for equity used during construction (AFUDC) for the years ended December 31, 2014, 2013, and 2012, respectively. AFUDC increased during 2014 due to the increase in spending on Constitution and various Transco expansion projects.

Provision_Benefit_for_Income_T

Provision (Benefit) for Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	Note 8 – Provision (Benefit) for Income Taxes
	The Provision (benefit) for income taxes includes:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Current:
	State	$	3		$	2		$	11

	Foreign	1			(22		)	26

		4			(20		)	37

	Deferred:
	State	8			15			—

	Foreign	17			35			5

		25			50			5

	Total provision (benefit)	$	29		$	30		$	42

	Reconciliations from the Provision (benefit) for income taxes at the federal statutory rate to the recorded Provision (benefit) for income taxes are as follows:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Provision at statutory rate	$	462		$	402		$	467

	Increases (decreases) in taxes resulting from:
	Income not subject to U.S. federal tax	(462		)	(402		)	(467		)
	State income taxes	11			17			11

	Foreign operations — net	18			13			31

	Provision (benefit) for income taxes	$	29		$	30		$	42

	The 2013 state deferred provision includes $14 million related to the impact of a second-quarter 2013 Texas franchise tax law change.
	Income before income taxes includes $72 million, $61 million, and $96 million of foreign income in 2014, 2013, and 2012, respectively.
	Deferred tax liabilities, primarily attributable to the taxable temporary differences from property, plant, and equipment, were $133 million, $117 million, and $72 million in 2014, 2013, and 2012, respectively.
	During 2014, we received cash refunds (net of payments) for income taxes of $28 million. Cash payments for income taxes (net of refunds) were $2 million and $54 million in 2013 and 2012, respectively, and are recorded in the Consolidated Balance Sheet.
	As of December 31, 2014, we do not have any material unrecognized tax benefits.
	Tax years after 2010 are subject to examination by the Texas Comptroller. Generally, tax returns for our Canadian entities are open to audit for tax years after 2010. Williams has indemnified us for any adjustments to foreign tax returns filed prior to the Canada Acquisition.

Benefit_Plans

Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2014
Employee Benefits and Share-based Compensation [Abstract]
Pension and Other Postretirement Benefits Disclosure [Text Block]	Note 9 – Benefit Plans
	Certain of the benefit costs charged to us by our general partners associated with employees who directly support us are described below. Additionally, allocated corporate expenses from Williams to us also include amounts related to these same employee benefits, which are not included in the amounts presented below. Employees supporting Pre-merger ACMP were not participants in the pension and other postretirement benefit plans sponsored by Williams during 2014. As a result, there are no pension and other postretirement benefit costs included in the amounts presented below associated with those employees. During 2014, employees supporting Pre-merger ACMP were eligible for defined contribution plans sponsored by the general partner of Pre-merger ACMP. The cost for the employer matching contributions for the period subsequent to July 1, 2014, is included in the defined contribution amount presented below. Effective January 1, 2015, these employees became Williams employees and eligible for certain employee benefit plans sponsored by Williams.
	Defined benefit pension plans
	Williams has noncontributory defined benefit pension plans (Williams Pension Plan, Williams Inactive Employees Pension Plan, and The Williams Companies Retirement Restoration Plan) that provide pension benefits for its eligible employees. Pension costs charged to us by Williams for 2014, 2013, and 2012 totaled $28 million, $44 million, and $41 million, respectively. At the total Williams plan level, the pension plans had a projected benefit obligation of $1.5 billion and $1.4 billion at December 31, 2014 and 2013, respectively. The plans were underfunded by $251 million and $143 million at December 31, 2014 and 2013, respectively.
	Postretirement benefits other than pensions
	Williams provides certain retiree health care and life insurance benefits for eligible participants. We recognized a net periodic postretirement benefit credited to us by Williams of $14 million and $4 million in 2014 and 2013, respectively, and a net periodic postretirement benefit cost charged to us by Williams of $4 million in 2012. At the total Williams plan level, the postretirement benefit plans had an accumulated postretirement benefit obligation of $233 million and $213 million at December 31, 2014 and 2013, respectively. The plans were underfunded by $25 million and $12 million at December 31, 2014 and 2013, respectively.
	Any differences between the annual expense and amounts currently being recovered in rates by Transco and Northwest Pipeline are recorded as an adjustment to expense and collected or refunded through future rate adjustments.
	Defined contribution plans
	We were charged compensation expense of $25 million, $16 million, and $19 million in 2014, 2013, and 2012, respectively, for contributions to these plans. The increase in expense in 2014 is primarily due to the impact of its acquisition of ACMP. (See Note 2 - Acquisitions.)

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories [Text Block]	Note 10 – Inventories


		December 31,

		2014		2013

		(Millions)

	Natural gas liquids, olefins, and natural gas in underground storage	$	150	$	111

	Materials, supplies, and other	81		83

		$	231	$	194

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Text Block]	Note 11 – Property, Plant and Equipment


		Estimated		Depreciation
		Useful Life (1)		Rates (1)	December 31,
		(Years)		(%)	2014			2013
					(Millions)
	Nonregulated:
	Natural gas gathering and processing facilities	5 - 40			$	18,717		$	9,172

	Construction in progress	Not applicable			2,115			2,727

	Other	3 - 45			1,459			964

	Regulated:
	Natural gas transmission facilities			1.2 - 6.97	10,867			10,633

	Construction in progress			Not applicable	985			273

	Other			1.35 - 33.33	1,336			1,293

	Total property, plant, and equipment, at cost				$	35,479		$	25,062

	Accumulated depreciation and amortization				(8,157		)	(7,437		)
	Property, plant, and equipment – net				$	27,322		$	17,625

	____________

	-1	Estimated useful life and depreciation rates are presented as of December 31, 2014. Depreciation rates for regulated assets are prescribed by the FERC.
	Depreciation and amortization expense for Property, plant, and equipment – net was $944 million, $729 million and $690 million in 2014, 2013, and 2012, respectively.
	Regulated Property, plant, and equipment – net includes approximately $746 million and $785 million at December 31, 2014 and 2013, respectively, related to amounts in excess of the original cost of the regulated facilities within our gas pipeline businesses as a result of our prior acquisitions. This amount is being amortized over 40 years using the straight-line amortization method. Current FERC policy does not permit recovery through rates for amounts in excess of original cost of construction.
	Asset Retirement Obligations
	Our accrued obligations relate to underground storage caverns, offshore platforms and pipelines, fractionation and compression facilities, gas gathering well connections and pipelines, and gas transmission facilities. At the end of the useful life of each respective asset, we are legally obligated to plug storage caverns and remove any related surface equipment, to restore land and remove surface equipment at gas processing, fractionation and compression facilities, to dismantle offshore platforms and appropriately abandon offshore pipelines, to cap certain gathering pipelines at the wellhead connection and remove any related surface equipment, and to remove certain components of gas transmission facilities from the ground.
	The following table presents the significant changes to our ARO:


		December 31,
		2014			2013
		(Millions)
	Beginning balance	$	561		$	579

	Liabilities incurred	101			8

	Liabilities settled (1)	(21		)	(31		)
	Accretion expense	44			53

	Revisions (2)	146			(48		)

	Ending balance	$	831		$	561

	______________

	-1	For 2014 and 2013, liabilities settled include $7 million and $25 million, respectively, related to the abandonment of certain of Transco’s natural gas storage caverns that are associated with a leak in 2010.


	-2	Several factors are considered in the annual review process, including inflation rates, current estimates for removal cost, discount rates, and the estimated remaining life of the assets. The 2014 revisions primarily reflect an increase in the estimated retirement costs for our offshore pipelines, an increase in the inflation rate and decreases in the discount rates used in the annual review process. The 2013 revision primarily reflects increases in the estimated remaining useful life of the assets. The 2013 revision also includes an increase of $9 million related to changes in the timing and method of abandonment on certain of Transco’s natural gas storage caverns that were associated with a leak in 2010.

	Transco is entitled to collect in rates the amounts necessary to fund its ARO. All funds received for such retirements are deposited into an external trust account dedicated to funding its ARO (ARO Trust). (See Note 16 – Fair Value Measurements, Guarantees, and Concentration of Credit Risk.) Under its current rate settlement Transco’s annual funding obligation is approximately $36 million, with installments to be deposited monthly.

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets Disclosure [Text Block]	Note 12 – Goodwill and Other Intangible Assets
	Goodwill
	Changes in the carrying amount of goodwill by reportable segment for the periods indicated are as follows:


		Access Midstream		Northeast G&P			Total
		(Millions)
	31-Dec-13	$	—	$	646		$	646

	Acquisition	474		—			474

	31-Dec-14	$	474	$	646		$	1,120

	Our goodwill is not subject to amortization, but is evaluated at least annually for impairment or more frequently if impairment indicators are present. We did not identify or recognize any impairments to goodwill in connection with our annual evaluation of goodwill for impairment (performed as of October 1) during the years ended December 31, 2014, 2013, and 2012. Following a significant decline in energy commodity prices and a decline in the fair value of Pre-merger ACMP's publicly-traded limited partner units, both in the fourth quarter of 2014, we performed an additional impairment evaluation as of December 31, 2014 of the goodwill recorded within the Access Midstream segment. In this evaluation, our estimate of the fair value of each reporting unit exceeded its carrying value and thus no impairment losses were recognized in 2014.
	Other Intangible Assets
	The gross carrying amount and accumulated amortization of Other intangible assets – net of accumulated amortization at December 31 are as follows:


		2014					2013
		Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
		(Millions)
	Contractual customer relationships	$	10,761	$	(310	)	$	1,747	$	(105	)

	Other intangible assets – net of accumulated amortization primarily relate to gas gathering, processing, and fractionation contractual customer relationships recognized in the ACMP, Laser, and Caiman acquisitions (See Note 2 – Acquisitions.) The intangible assets are being amortized on a straight-line basis over an initial period of 30 years which represents a portion of the term over which the contractual customer relationships are expected to contribute to our cash flows.
	We expense costs incurred to renew or extend the terms of our gas gathering, processing, and fractionation contracts with customers. Based on the estimated future revenues during the contract periods (as estimated at the time of the respective acquisition), the weighted-average periods prior to the next renewal or extension of the contractual customer relationships associated with the ACMP, Laser, and Caiman acquisitions were approximately 17 years, 9 years, and 18 years, respectively. Although a significant portion of the expected future cash flows associated with these contracts are dependent on our ability to renew or extend the arrangements beyond the initial contract periods, these expected future cash flows are significantly influenced by the scope and pace of our producer customers’ drilling programs. Once producer customers’ wells are connected to our gathering infrastructure, their likelihood of switching to another provider before the wells are abandoned is reduced due to the significant capital investment required.
	The amortization expense related to Other intangible assets – net of accumulated amortization was $207 million, $60 million and $43 million in 2014, 2013, and 2012, respectively. The estimated amortization expense for each of the next five succeeding fiscal years is approximately $357 million.

Debt_Banking_Arrangements_and_

Debt, Banking Arrangements, and Leases	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt Disclosure [Text Block]	Note 13 – Debt, Banking Arrangements, and Leases
	Long-Term Debt


			December 31,
			2014				2013
			(Millions)
	Unsecured:
	Transco:
	6.4% Notes due 2016		$	200			$	200

	6.05% Notes due 2018		250				250

	7.08% Debentures due 2026		8				8

	7.25% Debentures due 2026		200				200

	5.4% Notes due 2041		375				375

	4.45% Notes due 2042		400				400

	Northwest Pipeline:
	7% Notes due 2016		175				175

	5.95% Notes due 2017		185				185

	6.05% Notes due 2018		250				250

	7.125% Debentures due 2025		85				85

	Williams Partners L.P.:
	3.8% Notes due 2015 (3)		750				750

	7.25% Notes due 2017		600				600

	5.25% Notes due 2020		1,500				1,500

	4.125% Notes due 2020		600				600

	5.875% Notes due 2021 (1)		750				—

	4% Notes due 2021		500				500

	3.35% Notes due 2022		750				750

	6.125% Notes due 2022 (1)		750				—

	4.875% Notes due 2023 (1)		1,400				—

	4.5% Notes due 2023		600				600

	4.3% Notes due 2024		1,000				—

	4.875% Notes due 2024 (1)		750				—

	3.9% Notes due 2025		750				—

	6.3% Notes due 2040		1,250				1,250

	5.8% Notes due 2043		400				400

	5.4% Notes due 2044		500				—

	4.9% Notes due 2045		500				—

Pre-merger ACMP Credit facility loans (1)		640				—

Capital lease obligations		5				—

Net unamortized debt premium (discount) (2)		207				(21		)

Long-term debt, including current portion		16,330				9,057

Long-term debt due within one year		(4		)		—

Long-term debt		$	16,326			$	9,057

______________________________________________________
(1) These notes and credit facility loans are associated with Pre-merger ACMP. See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies and Note 2 – Acquisitions.
(2) Includes premium related to the fair value of Pre-merger ACMP debt. See Note 2 – Acquisitions.

-3	Presented as long-term debt due to our intent and ability to refinance.
The terms of our senior unsecured notes are governed by indentures that contain covenants that, among other things, limit: (1) our ability and the ability of our subsidiaries to create liens securing indebtedness and (2) mergers, consolidations, and sales of assets. The indentures also contain customary events of default, upon which the trustee or the holders of the senior unsecured notes may declare all outstanding senior unsecured notes to be due and payable immediately.
The following table presents aggregate minimum maturities of long-term debt, excluding net unamortized debt premium (discount) and capital lease obligations, for each of the next five years:


	December 31,
	2014
	(Millions)
2015	$	—

2016	375

2017	785

2018	1,140

2019	—

Issuances and retirements
We retired $750 million of 3.8 percent senior unsecured notes that matured on February 15, 2015.
On June 27, 2014, Pre-merger WPZ completed a public offering of $750 million of 3.9 percent senior unsecured notes due 2025 and $500 million of 4.9 percent senior unsecured notes due 2045. Pre-merger WPZ used the net proceeds to repay amounts outstanding under its commercial paper program, to fund capital expenditures, and for general partnership purposes.
On March 4, 2014, Pre-merger WPZ completed a public offering of $1 billion of 4.3 percent senior unsecured notes due 2024 and $500 million of 5.4 percent senior unsecured notes due 2044. Pre-merger WPZ used the net proceeds to repay amounts outstanding under its commercial paper program, to fund capital expenditures, and for general partnership purposes.
On November 15, 2013, Pre-merger WPZ completed a public offering of $600 million of 4.5 percent senior unsecured notes due 2023 and $400 million of 5.8 percent senior unsecured notes due 2043. Pre-merger WPZ used the net proceeds to repay amounts outstanding under its commercial paper program, to fund capital expenditures, and for general partnership purposes.
Credit Facilities


	31-Dec-14
	Available				Outstanding
	(Millions)
Pre-merger WPZ credit facility (1)(3)
Loans	$	2,500			$	—

Letters of credit sub-limit	1,300				—

Letters of credit under certain bilateral bank agreements					1

Pre-merger ACMP credit facility (2)
Loans	1,750				640

Letters of credit sub-limit	200				2

Swing line advances sub-limit	100				—

________________

-1	Under certain conditions, the amount available may be increased up to an additional $500 million.

-2	Under certain conditions, the amount available may be increased up to an additional $250 million.

-3	Transco and Northwest Pipeline are each able to borrow up to $500 million under this credit facility to the extent not otherwise utilized by the other co-borrowers.
The agreements governing credit facilities for Pre-merger WPZ and Pre-merger ACMP contain the following terms and conditions:

•	Various covenants may limit, among other things, a borrower’s and its material subsidiaries’ ability to grant certain liens supporting indebtedness, a borrower’s ability to merge or consolidate, sell all or substantially all of its assets, enter into certain affiliate transactions, make certain distributions during an event of default, make investments, and allow any material change in the nature of its business.

•	If an event of default with respect to a borrower occurs under the credit facility, the lenders will be able to terminate the commitments for all borrowers and accelerate the maturity of any loans of the defaulting borrower under the credit facility agreement and exercise other rights and remedies.

•	Each time funds are borrowed under Pre-merger WPZ’s credit facility, the applicable borrower could choose from two methods of calculating interest: a fluctuating base rate equal to the bank’s alternate base rate plus an applicable margin or a periodic fixed rate equal to LIBOR plus an applicable margin. The borrower was required to pay a commitment fee based on the unused portion of the credit facility. The applicable margin and the commitment fee were determined for each borrower by reference to a pricing schedule based on such borrower’s senior unsecured long-term debt ratings.

•	Each time funds are borrowed under Pre-merger ACMP’s credit facility, it may choose from two methods of calculating interest: (1) the greater of (a) the reference rate of Wells Fargo Bank, NA, (b) the federal funds effective rate plus 0.50 percent or (c) the Eurodollar rate which is based on LIBOR plus 1.00 percent, each of which is subject to a margin that varies from 0.50 percent to 1.50 percent, according to its leverage ratio (as defined in the agreement), or (2) the Eurodollar rate plus a margin that varies from 1.50 percent to 2.50 percent, according to its leverage ratio. The revolving credit facility is secured by all of Pre-merger ACMP’s assets. If Pre-merger ACMP reaches investment grade status, it will have the option to release the security under the credit facility and amounts borrowed will bear interest under a specified ratings-based pricing grid. Pre-merger ACMP is required to pay a commitment fee based on the unused portion of its respective credit facility of (a) 0.25 percent to 0.375 percent while it is subject to the leverage-based pricing grid, according to its leverage ratio and (b) 0.15 percent to 0.30 percent while it is subject to the ratings-based pricing grid, according to its senior unsecured long-term debt ratings.
Pre-merger WPZ credit facility
On December 1, 2014, Pre-merger WPZ, Transco, Northwest Pipeline, the lenders named therein and an administrative agent entered into Amendment No.1 and Consent to the First Amended & Restated Credit Agreement, dated as of July 31, 2013. The amendment provided the consent of the lenders for this credit agreement to continue for Pre-merger ACMP upon consummation of the merger and the termination of Pre-merger ACMP’s existing credit agreement. In addition, the amendment provided the consent that certain existing liens and guarantees of indebtedness of Pre-merger ACMP to be terminated in connection with the merger would not become liens and guarantees of indebtedness under this credit agreement.
On February 2, 2015, the Pre-merger WPZ credit facility was terminated in connection with the merger.
Pre-merger ACMP credit facility
On February 2, 2015, Pre-merger ACMP credit facility loans outstanding were paid and terminated in connection with the merger.
Credit facilities post-merger
On February 2, 2015, we along with Transco, Northwest Pipeline, the lenders named therein and an administrative agent entered into the Second Amended & Restated Credit Agreement with aggregate commitments available of $3.5 billion, with up to an additional $500 million increase in aggregate commitments available under certain circumstances. The maturity date of the facility is February 2, 2020. However, the co-borrowers may request an extension of the maturity date for an additional one year period, up to two times, to allow a maturity date as late as February 2, 2022, under certain circumstances. The agreement allows for swing line loans up to an aggregate amount of $150 million, subject to available capacity under the credit facility, and letters of credit commitments of $1.125 billion. Transco and Northwest Pipeline are each able to borrow up to $500 million under this credit facility to the extent not otherwise utilized by the other co-borrowers.
The agreement governing our credit facility contains the following terms and conditions:

•	Various covenants may limit, among other things, a borrower’s and its material subsidiaries’ ability to grant certain liens supporting indebtedness, a borrower’s ability to merge or consolidate, sell all or substantially all of its assets, enter into certain affiliate transactions, make certain distributions during an event of default, enter into certain restrictive agreements, and allow any material change in the nature of its business.

•	If an event of default with respect to a borrower occurs under the credit facility, the lenders will be able to terminate the commitments for all borrowers and accelerate the maturity of any loans of the defaulting borrower under the credit facility agreement and exercise other rights and remedies.

•	Other than swingline loans, each time funds are borrowed, the borrower must choose whether such borrowing will be an alternate base rate borrowing or a Eurodollar borrowing. If such borrowing is an alternate base rate borrowing, interest is calculated on the basis of the greater of (a) the Prime Rate, (b) the Federal Funds Effective Rate plus ½ of 1 percent and (c) a periodic fixed rate equal to the London Interbank Offered Rate (LIBOR) plus 1 percent, plus, in the case of each of (a), (b) and (c), an applicable margin. If the borrowing is a Eurodollar borrowing, interest is calculated on the basis of LIBOR for the relevant period plus an applicable margin. Interest on swingline loans is calculated as the sum of the alternate base rate plus an applicable margin. The borrower is required to pay a commitment fee based on the unused portion of the credit facility. The applicable margin and the commitment fee are determined for each borrower by reference to a pricing schedule based on such borrower’s senior unsecured long-term debt ratings.
Our significant financial covenants require:

•	The ratio of debt to EBITDA (each as defined in the credit facility) to be no greater than 5 to 1, except for the fiscal quarter and the two following fiscal quarters in which one or more acquisitions has been executed, in which case the ratio of debt to EBITDA is to be no greater than 5.5 to 1.

•	The ratio of debt to capitalization (defined as net worth plus debt) must be no greater than 65 percent for each of Transco and Northwest Pipeline.
On February 3, 2015, we entered into a Credit Agreement providing for a $1.5 billion short-term credit facility with a maturity date of August 3, 2015 with an option to extend the maturity date to February 2, 2016 subject to certain circumstances. Our short-term credit facility has substantially the same financial covenants as our $3.5 billion credit facility. Under our short-term credit facility any time funds are borrowed, we must choose whether such borrowing will be an alternate base rate borrowing or a Eurodollar borrowing. Interest is calculated on each of these types of borrowings in the same manner as under our $3.5 billion credit facility. We are required to pay a commitment fee based on the unused portion of the short-term credit facility. The applicable margin and the commitment fee are determined by reference to a pricing schedule based on our senior unsecured long-term debt ratings. In the event of certain debt incurrences, issuances of equity, and certain asset sales, we will be required to repay any outstanding borrowings and the commitments under the short-term facility will be reduced on a dollar-for-dollar basis with the net cash proceeds of such events.
We are in compliance with these financial covenants as measured at December 31, 2014.
As of February 24, 2015, $1.3 billion is outstanding under our long-term credit facility.
Commercial Paper Program
Pre-merger WPZ’s commercial paper program allows a maximum outstanding amount at any time of $2 billion of unsecured commercial paper notes. The maturities of the commercial paper notes vary but may not exceed 397 days from the date of issuance. The commercial paper notes are sold under customary terms in the commercial paper market and are issued at a discount from par, or, alternatively, are sold at par and bear varying interest rates on a fixed or floating basis. Proceeds from these notes are used for general partnership purposes, including funding capital expenditures, working capital, and partnership distributions. We classify commercial paper outstanding in Current liabilities in the Consolidated Balance Sheet, as the outstanding notes at December 31, 2014 and December 31, 2013, having maturity dates less than three months from the date of issuance. At December 31, 2014, $798 million of Commercial paper is outstanding at a weighted average interest rate of 0.92 percent. At December 31, 2013, $225 million of Commercial paper is outstanding at a weighted average interest rate of 0.42 percent.
On February 2, 2015, we amended and restated the commercial paper program for the merger and to allow a maximum outstanding amount of $3 billion of unsecured commercial paper notes. As of February 24, 2015, $1.8 billion is outstanding under this program.

Cash Payments for Interest (Net of Amounts Capitalized)
Cash payments for interest (net of amounts capitalized) were $499 million in 2014, $366 million in 2013, and $381 million in 2012.
Leases-Lessee
The future minimum annual rentals under noncancelable operating leases, are payable as follows:


	December 31,
	2014
	(Millions)
2015	$	72

2016	62

2017	49

2018	37

2019	33

Thereafter	129

Total	$	382

Total rent expense was $101 million in 2014, $51 million in 2013, and $46 million in 2012 and primarily included in Operating and maintenance expenses and Selling, general, and administrative expenses in the Consolidated Statement of Comprehensive Income.

Partners_Capital

Partners' Capital	12 Months Ended
Partners' Capital	Dec. 31, 2014
Partners' Capital Notes [Abstract]
Unit Transactions Disclosure [Text Block]	Note 14 – Partners’ Capital
	Limited partner units presented on the Consolidated Balance Sheet have been adjusted in accordance with the exchange ratios pursuant to the terms of the Merger. (See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.)
	The partners’ equity interests in Pre-merger ACMP as of July 1, 2014, have been presented within the capital account of the general partner for interests owned by Williams and noncontrolling interests for interests held by the public as a Contribution from The Williams Companies, Inc. – net within the Consolidated Statement of Changes in Equity. Additionally, activity associated with the partners’ equity interests in Pre-merger ACMP during the period under common control has been presented accordingly within the capital account of the general partner for the interests owned by Williams or noncontrolling interests for interests held by the public. The Pre-merger ACMP partners’ equity includes limited partner common units and Class B units. These Class B units are held by an affiliate of our general partner and receive additional paid-in-kind units in lieu of cash distributions. Each Class B unit became convertible into common units on a one-for-one basis following our distribution paid to unitholders in February 2015.
	Transactions which occurred prior to the Merger during 2014 and 2013 are summarized below:
	In August 2014, Pre-merger WPZ issued 1,080,448 Pre-merger WPZ common units pursuant to an equity distribution agreement between Pre-merger WPZ and certain banks. The net proceeds of $55 million were used for general partnership purposes. Pre-merger WPZ incurred commission fees of $554 thousand associated with these transactions.
	In March 2013, Pre-merger WPZ completed an equity issuance of 14,250,000 Pre-merger WPZ common units, including 3,000,000 Pre-merger WPZ common units sold to Williams in a private placement. Subsequently, the underwriters exercised their option to purchase an additional 1,687,500 Pre-merger WPZ common units. The net proceeds of approximately $760 million were used to repay amounts outstanding under Pre-merger WPZ’s credit facility.
	In August 2013, Pre-merger WPZ completed an equity issuance of 21,500,000 Pre-merger WPZ common units. Subsequently, the underwriters exercised their option to purchase an additional 3,225,000 Pre-merger WPZ common units. The net proceeds of approximately $1.2 billion were used to repay amounts outstanding under Pre-merger WPZ’s commercial paper program, to fund capital expenditures and for general partnership purposes.
	Limited Partners’ Rights
	Significant rights of the limited partners include the following:

	•	Right to receive distributions of available cash within 45 days after the end of each quarter.

	•	No limited partner shall have any management control over our business and affairs; the general partner shall conduct, direct and manage our activities.

	•	The general partner may be removed if such removal is approved by the unitholders holding at least 66 2/3 percent of the outstanding units voting as a single class, including units held by our general partner and its affiliates.
	Incentive Distribution Rights
	Our general partner is entitled to incentive distributions if the amount we distribute to unitholders with respect to any quarter exceeds specified target levels shown below:


			Total Quarterly Distribution per unit (1)	Unitholders (1)	General
			Total Quarterly Distribution per unit (1)	Unitholders (1)	Partner (1)
	Minimum Quarterly Distribution		$0.34	98%	2%
	First Target Distribution		Up to $0.388125	98	2
	Second Target Distribution		Above $0.388125 up to $0.421875	85	15
	Third Target Distribution		Above $0.421875 up to $0.50625	75	25
	Thereafter		Above $0.50625	50	50
	_____________

	-1	Table reflects the completion of the Merger. See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.
	The table above assumes that the Partnership’s general partner maintains its two percent general partner interest, that there are no arrearages on common units and the general partner continues to own the IDRs. The maximum distribution sharing percentage of 50 percent includes distributions paid to the general partner on its two percent general partner interest and does not include any distributions that the general partner may receive on limited partner units that it owns or may acquire.
	In the event of liquidation, all property and cash in excess of that required to discharge all liabilities will be distributed to the unitholders and our general partner in proportion to their capital account balances, as adjusted to reflect any gain or loss upon the sale or other disposition of our assets in liquidation.
	Issuances of Additional Partnership Securities
	Our partnership agreement allows us to issue additional partnership securities for any partnership purpose at any time and from time to time for consideration and on terms and conditions as our general partner determines, all without the approval of any limited partners.

EquityBased_Compensation_Notes

Equity-Based Compensation (Notes)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation [Text Block]	Note 15 – Equity-Based Compensation
	Williams Plan Information
	The Williams Companies, Inc. 2007 Incentive Plan (Plan) provides for Williams common-stock-based awards to both employees and nonmanagement directors. The Plan permits the granting of various types of awards including, but not limited to, stock options and restricted stock units. Awards may be granted for no consideration other than prior and future services or based on certain financial performance targets being achieved.
	Williams bills us directly for compensation expense related to stock-based compensation awards based on the fair value of the awards.
	Operating and maintenance expenses and Selling, general, and administrative expenses include equity-based compensation expense for the years ended December 31, 2014, 2013, and 2012 of $14 million, $12 million and $13 million, respectively.
	Pre-merger ACMP Plan Information
	Certain employees of Pre-merger ACMP’s general partner received equity-based compensation through Pre-merger ACMP’s equity-based compensation programs. The fair value of the awards issued was determined based on the fair market value of the units of Pre-merger ACMP on the date of grant. This value is being amortized over the vesting period, which is from one to four years from the date of grant. Beginning in 2015 certain of these employees will transition to our equity-based compensation plans. No additional awards of units through Pre-merger ACMP’s equity-based compensation programs are expected. Included in Operating and maintenance expenses; Selling, general, and administrative expenses; and Equity earnings (losses) is equity-based compensation expense of $11 million in 2014 related to Pre-merger ACMP’s equity-based compensation program. As of December 31, 2014, there was $65 million of unrecognized compensation expense attributable to the outstanding awards, which does not include the effect of estimated forfeitures of $6 million. These amounts are expected to be recognized over a weighted average period of 2.3 years.
	The following summary reflects nonvested restricted stock unit activity for awards issued by Pre-merger ACMP and related information for the six months ended December 31, 2014:


	Restricted Stock Units Outstanding	Units	Weighted-
			Average
			Fair Value
		(Millions)
	Granted	1.3	$	59.67

	Forfeited	—	$	63.89

	Vested	—	$	63.75

	Nonvested at December 31, 2014	1.3	$	59.35

Fair_Value_Measurements_Guaran

Fair Value Measurements Guarantees and Concentration of Credit Risk	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements Guarantees and Concentration of Credit Risk [Text Block]	Note 16 – Fair Value Measurements, Guarantees, and Concentration of Credit Risk
	The following table presents, by level within the fair value hierarchy, certain of our financial assets and liabilities. The carrying values of cash and cash equivalents, accounts receivable, commercial paper, and accounts payable approximate fair value because of the short-term nature of these instruments. Therefore, these assets and liabilities are not presented in the following table.


									Fair Value Measurements Using
		Carrying				Fair			Quoted		Significant			Significant
		Amount				Value			Prices In		Other			Unobservable
									Active		Observable			Inputs
									Markets for		Inputs			(Level 3)
									Identical		(Level 2)
									Assets
									(Level 1)
		(Millions)
	Assets (liabilities) at December 31, 2014:
	Measured on a recurring basis:
	ARO Trust investments	$	48			$	48		$	48	$	—		$	—

	Energy derivatives assets not designated as hedging instruments	3				3			1		—			2

	Energy derivatives liabilities not designated as hedging instruments	(2		)		(2		)	—		—			(2		)

	Additional disclosures:
	Notes receivable and other	5				4			—		4			—

	Long-term debt, including current portion (1)	(16,325		)		(16,607		)	—		(16,607		)	—

	Assets (liabilities) at December 31, 2013:
	Measured on a recurring basis:
	ARO Trust investments	$	33			$	33		$	33	$	—		$	—

	Energy derivatives assets not designated as hedging instruments	3				3			—		—			3

	Energy derivatives liabilities not designated as hedging instruments	(3		)		(3		)	—		(1		)	(2		)

	Additional disclosures:
	Notes receivable and other	7				7			1		6			—

	Long-term debt, including current portion	(9,057		)		(9,581		)	—		(9,581		)	—

	______________
	(1) Excludes capital leases
	Fair Value Methods
	We use the following methods and assumptions in estimating the fair value of our financial instruments:
	Assets and liabilities measured at fair value on a recurring basis
	ARO Trust investments: Transco deposits a portion of its collected rates, pursuant to its rate case settlement, into an external trust (ARO Trust) that is specifically designated to fund future asset retirement obligations. The ARO Trust invests in a portfolio of actively traded mutual funds that are measured at fair value on a recurring basis based on quoted prices in an active market, is classified as available-for-sale, and is reported in Regulatory assets, deferred charges, and other in the Consolidated Balance Sheet. Both realized and unrealized gains and losses are ultimately recorded as regulatory assets or liabilities.
	Energy derivatives: Energy derivatives include commodity based exchange-traded contracts and over-the-counter (OTC) contracts, which consist of physical forwards, futures, and swaps that are measured at fair value on a recurring basis. The fair value amounts are presented on a gross basis and do not reflect the netting of asset and liability positions permitted under the terms of our master netting arrangements. Further, the amounts do not include cash held on deposit in margin accounts that we have received or remitted to collateralize certain derivative positions. Energy derivatives assets are reported in Other current assets and Regulatory assets, deferred charges, and other in the Consolidated Balance Sheet. Energy derivatives liabilities are reported in Other accrued liabilities and Regulatory liabilities, deferred income, and other in the Consolidated Balance Sheet.
	Reclassifications of fair value between Level 1, Level 2, and Level 3 of the fair value hierarchy, if applicable, are made at the end of each quarter. No transfers between Level 1 and Level 2 occurred during the years ended December 31, 2014 or 2013.
	Additional fair value disclosures
	Notes receivable and other: The disclosed fair value of our notes receivable is primarily determined by an income approach which considers the underlying contract amounts and our assessment of our ability to recover these amounts. The current portion is reported in Trade accounts and notes receivable – net, and the noncurrent portion is reported in Regulatory assets, deferred charges, and other in the Consolidated Balance Sheet.
	Long-term debt: The disclosed fair value of our long-term debt is determined by a market approach using broker quoted indicative period-end bond prices. The quoted prices are based on observable transactions in less active markets for our debt or similar instruments.
	Assets and liabilities measured at fair value on a nonrecurring basis
	During 2014, we designated certain equipment within our Northeast G&P segment as held for sale. The estimated fair value (less cost to sell) of the equipment at December 31, 2014, is $32 million and is reported in Other current assets in the Consolidated Balance Sheet. The estimated fair value was determined by a market approach based on our analysis of information related to sales of similar pre-owned equipment in the principal market. This analysis resulted in impairment charges of $27 million, recorded in Other (income) expense – net within Costs and expenses. This nonrecurring fair value measurement fell within Level 3 of the fair value hierarchy.
	In December 2014, certain materials and equipment within our Access Midstream segment was designated as held for sale. The estimated fair value (less cost to sell) of the equipment at December 31, 2014, is $1 million and is reported in Other current assets in the Consolidated Balance Sheet. The estimated fair value was determined by a market approach based on our analysis of information related to sales of similar pre-owned equipment in the principal market. This analysis resulted in an impairment charge of $12 million, which is included in Other (income) expense – net within Costs and expenses. This nonrecurring fair value measurement fell within Level 3 of the fair value hierarchy.
	Guarantees
	We are required by our revolving credit agreements to indemnify lenders for certain taxes required to be withheld from payments due to the lenders and for certain tax payments made by the lenders. The maximum potential amount of future payments under these indemnifications is based on the related borrowings and such future payments cannot currently be determined. These indemnifications generally continue indefinitely unless limited by the underlying tax regulations and have no carrying value. We have never been called upon to perform under these indemnifications and have no current expectation of a future claim.
	Concentration of Credit Risk
	Cash equivalents
	Our cash equivalents are primarily invested in funds with high-quality, short-term securities and instruments that are issued or guaranteed by the U.S. government.
	Accounts and notes receivable
	The following table summarizes concentration of receivables, net of allowances.


		December 31,
		2014				2013
	(Millions)
NGLs, natural gas, and related products and services	$	728			$	341

Transportation of natural gas and related products	175				193

Other	2				34

Total	$	905			$	568

Customers include producers, distribution companies, industrial users, gas marketers and pipelines primarily located in the continental United States and Canada. As a general policy, collateral is not required for receivables, but customers’ financial condition and credit worthiness are evaluated regularly. On December 31, 2014, one customer accounted for $308 million of the consolidated Accounts and notes receivable balance.
Revenues
In 2014, 2013 and 2012, we had one customer in our NGL & Petchem Services segment that accounted for 5 percent, 9 percent, and 14 percent of our consolidated revenues, respectively. In 2014, we also had one customer, primarily within our Access Midstream segment, that accounted for 9 percent of our consolidated revenues.

Contingent_Liabilities

Contingent Liabilities	12 Months Ended
Contingent Liabilities	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Contingent Liabilities [Text Block]	Note 17 – Contingent Liabilities and Commitments
	Environmental Matters
	We are a participant in certain environmental activities in various stages including assessment studies, cleanup operations and remedial processes at certain sites, some of which we currently do not own. We are monitoring these sites in a coordinated effort with other potentially responsible parties, the U.S. Environmental Protection Agency (EPA), and other governmental authorities. We are jointly and severally liable along with unrelated third parties in some of these activities and solely responsible in others. Certain of our subsidiaries have been identified as potentially responsible parties at various Superfund and state waste disposal sites. In addition, these subsidiaries have incurred, or are alleged to have incurred, various other hazardous materials removal or remediation obligations under environmental laws. As of December 31, 2014, we have accrued liabilities totaling $19 million for these matters, as discussed below. Our accrual reflects the most likely costs of cleanup, which are generally based on completed assessment studies, preliminary results of studies or our experience with other similar cleanup operations. Certain assessment studies are still in process for which the ultimate outcome may yield significantly different estimates of most likely costs. Any incremental amount in excess of amounts currently accrued cannot be reasonably estimated at this time due to uncertainty about the actual number of contaminated sites ultimately identified, the actual amount and extent of contamination discovered and the final cleanup standards mandated by the EPA and other governmental authorities.
	The EPA and various state regulatory agencies routinely promulgate and propose new rules, and issue updated guidance to existing rules. More recent rules and rulemakings include, but are not limited to, rules for reciprocating internal combustion engine maximum achievable control technology, new air quality standards for ground level ozone, one hour nitrogen dioxide emission limits, and new air quality standards impacting storage vessels, pressure valves, and compressors. We are unable to estimate the costs of asset additions or modifications necessary to comply with these new regulations due to uncertainty created by the various legal challenges to these regulations and the need for further specific regulatory guidance.
	Our interstate gas pipelines are involved in remediation activities related to certain facilities and locations for polychlorinated biphenyls, mercury, and other hazardous substances. These activities have involved the EPA and various state environmental authorities, resulting in our identification as a potentially responsible party at various Superfund waste sites. At December 31, 2014, we have accrued liabilities of $11 million for these costs. We expect that these costs will be recoverable through rates.
	We also accrue environmental remediation costs for natural gas underground storage facilities, primarily related to soil and groundwater contamination. At December 31, 2014, we have accrued liabilities totaling $8 million for these costs.
	Geismar Incident
	As a result of the previously discussed Geismar Incident, there were two fatalities and numerous individuals (including employees and contractors) reported injuries, which varied from minor to serious. We are addressing the following matters in connection with the Geismar Incident.
	On June 28, 2013, the Louisiana Department of Environmental Quality (LDEQ) issued a Consolidated Compliance Order & Notice of Potential Penalty that consolidates claims of unpermitted emissions and other deviations under the Clean Air Act that the parties had been negotiating since 2010 and alleged unpermitted emissions arising from the Geismar Incident. On November 12, 2014, the LDEQ issued a Notice of Potential Penalty for the alleged violations. LDEQ then issued a Penalty Assessment on November 21, 2014. We paid a penalty of $194,306 on December 1, 2014.
	On October 21, 2013, the EPA issued an Inspection Report pursuant to the Clean Air Act’s Risk Management Program following its inspection of the facility on June 24 through 28, 2013. The report notes the EPA’s preliminary determinations about the facility’s documentation regarding process safety, process hazard analysis, as well as operating procedures, employee training, and other matters. On June 16, 2014, we received a request for information related to the Geismar Incident from the EPA under Section 114 of the Clean Air Act to which we responded on August 13, 2014. The EPA could issue penalties pertaining to final determinations.
	On December 11, 2013, the Occupational Safety and Health Administration (OSHA) issued citations in connection with its investigation of the June 13, 2013 incident, which included a Notice of Penalty for $99,000. We settled the citations with OSHA on September 12, 2014 for a penalty of $36,000. The settlement was judicially approved on September 23, 2014, and the order approving settlement became a final order on November 10, 2014. On June 25, 2013, OSHA commenced a second inspection pursuant to its Refinery and Chemical National Emphasis Program (NEP). OSHA did not issue a citation in connection with this NEP inspection and there is a six-month statute of limitations for violation of the Occupational Safety and Health Act of 1970 or regulations promulgated under such act.
	Additionally, multiple lawsuits, including class actions for alleged offsite impacts, property damage, customer claims, and personal injury, have been filed against various of our subsidiaries. Due to ongoing litigation concerning defenses to liability and limited information as to the nature and extent of plaintiffs’ damages, we cannot reasonably estimate a range of potential loss related to these contingencies at this time.
	Royalty Matters
	Certain of our customers, including one major customer, have been named in various lawsuits alleging underpayment of royalty. In certain of these cases, we have also been named as a defendant based on allegations that we improperly participated with that major customer in causing the alleged royalty underpayments. We have also received subpoenas from the United States Department of Justice and the Pennsylvania Attorney General requesting documents relating to the agreements between us and our major customer and calculations of the major customer’s royalty payments. We believe that the claims asserted to date are subject to indemnity obligations owed to us by that major customer. Due to the preliminary status of the cases, we are unable to estimate a range of liability at this time.
	Other
	In addition to the foregoing, various other proceedings are pending against us which are incidental to our operations.
	Summary
	We estimate that for all matters for which we are able to reasonably estimate a range of loss, including those noted above and others that are not individually significant, our aggregate reasonably possible losses beyond amounts accrued for all of our contingent liabilities are immaterial to our expected future annual results of operations, liquidity, and financial position. These calculations have been made without consideration of any potential recovery from third parties. We disclose all significant matters for which we are unable to reasonably estimate a range of possible loss.
	Commitments
	Commitments for construction and acquisition of property, plant and equipment are approximately $552 million at December 31, 2014.

Segment_Disclosures

Segment Disclosures	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Disclosures [Text Block]	Note 18 – Segment Disclosures
	Our reportable segments are Access Midstream, Northeast G&P, Atlantic-Gulf, West, and NGL & Petchem Services. (See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.)
	Performance Measurement
	As of December 31, 2014, we evaluate segment operating performance based on Segment profit (loss) from operations, which includes Segment revenues from external and internal customers, segment costs and expenses, Equity earnings (losses) and Income (loss) from investments. General corporate expenses represent Selling, general, and administrative expenses that are not allocated to our segments. The accounting policies of the segments are the same as those described in Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies. Intersegment revenues primarily represent the sale of NGLs from our natural gas processing plants to our marketing business and are generally accounted for at current market prices as if the sales were to unaffiliated third parties.
	The following geographic area data includes Revenues from external customers based on product shipment origin and Long-lived assets based upon physical location.


				United States				Canada				Total
				(Millions)
	Revenues from external customers:
		2014		$	7,212			$	197			$	7,409

		2013		6,685				150				6,835

		2012		7,320				151				7,471


	Long-lived assets:
		2014		$	37,798			$	1,095			$	38,893

		2013		18,776				1,137				19,913

		2012		16,637				870				17,507

	Long-lived assets are comprised of property, plant, and equipment, goodwill, and other intangible assets.
	The following table reflects the reconciliation of Segment revenues and Segment profit (loss) to Total revenues and Operating income as reported in the Consolidated Statement of Comprehensive Income. It also presents other financial information related to long-lived assets.


		Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
						G&P				Gulf							Petchem
																	Services
		(Millions)

	2014
	Segment revenues:

	Service revenues

	External	$	781			$	450			$	1,497			$	1,034		$	126		$	—			$	3,888

	Internal	—				1				4				—			—			(5		)		—

	Total service revenues	781				451				1,501				1,034			126			(5		)		3,888

	Product sales
	External	—				225				499				70			2,727			—				3,521

	Internal	—				5				354				476			259			(1,094		)		—

	Total product sales	—				230				853				546			2,986			(1,094		)		3,521

	Total revenues	$	781			$	681			$	2,354			$	1,580		$	3,112		$	(1,099	)		$	7,409

	Segment profit (loss)	$	265			$	212			$	635			$	631		$	265						$	2,008

	Less equity earnings (losses)	96				19				76				—			37							228

	Segment operating income (loss)	$	169			$	193			$	559			$	631		$	228						1,780

	General corporate expenses																							(171		)
	Operating income																							$	1,609


	Other financial information:
Depreciation and amortization	$	296			$	170			$	379			$	239		$	67						$	1,151


2013
Segment revenues:
Service revenues
External	$	—			$	335			$	1,414			$	1,053		$	112		$	—			$	2,914

Internal	—				—				10				1			—			(11		)		—

Total service revenues	—				335				1,424				1,054			112			(11		)		2,914

Product sales
External	—				166				830				64			2,861			—				3,921

Internal	—				—				95				708			294			(1,097		)		—

Total product sales	—				166				925				772			3,155			(1,097		)		3,921

Total revenues	$	—			$	501			$	2,349			$	1,826		$	3,267		$	(1,108	)		$	6,835

Segment profit (loss)	$	—			$	(24	)		$	614			$	741		$	346						$	1,677

Less:
Equity earnings (losses)	—				(7		)		72				—			39							104

Income (loss) from investments	—				—				—				—			(3		)					(3		)

Segment operating income (loss)	$	—			$	(17	)		$	542			$	741		$	310						1,576

General corporate expenses																							(169		)
Operating income																							$	1,407


Other financial information:
Depreciation and amortization	$	—			$	132			$	363			$	236		$	60						$	791




	Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
					G&P				Gulf							Petchem
																Services
	(Millions)

2012
Segment revenues:
Service revenues
External	$	—			$	168			$	1,371			$	1,067		$	108		$	—			$	2,714

Internal	—				—				12				5			—			(17		)		—

Total service revenues	—				168				1,383				1,072			108			(17		)		2,714

Product sales
External	—				2				709				40			4,006			—				4,757

Internal	—				—				363				1,089			258			(1,710		)		—

Total product sales	—				2				1,072				1,129			4,264			(1,710		)		4,757

Total revenues	$	—			$	170			$	2,455			$	2,201		$	4,372		$	(1,727	)		$	7,471

Segment profit (loss)	$	—			$	(37	)		$	574			$	980		$	390						$	1,907

Less:
Equity earnings (losses)	—				(23		)		92				—			42							111

Income (loss) from investments	—				—				—				—			(4		)					(4		)

Segment operating income (loss)	$	—			$	(14	)		$	482			$	980		$	352						1,800

General corporate expenses																							(190		)
Operating income																							$	1,610


Other financial information:
Depreciation and amortization	$	—			$	76			$	381			$	234		$	43						$	734


Revenues by service that exceeded 10 percent of consolidated revenue include:


	Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
					G&P				Gulf							Petchem
																Services
	(Millions)
2014
Service:
Regulated natural gas transportation and storage	$	—			$	—			$	1,313			$	470		$	—		$	(2	)		$	1,781

Gathering & processing	781				394				79				544			—			(2		)		1,796


2013
Service:
Regulated natural gas transportation and storage	$	—			$	—			$	1,244			$	469		$	—		$	(9	)		$	1,704

Gathering & processing	—				302				70				562			—			(2		)		932


2012
Service:
Regulated natural gas transportation and storage	$	—			$	—			$	1,171			$	438		$	—		$	(11	)		$	1,598

Gathering & processing	—				159				80				607			—			(2		)		844

The following table reflects Total assets, Investments, and Additions to long-lived assets by reportable segments:


	Total Assets at December 31,								Investments at December 31,							Additions to Long-Lived Assets at December 31,
	2014				2013				2014				2013			2014			2013				2012
	(Millions)
Access Midstream (1)	$	23,024			$	—			$	6,004			$	—		$	16,964		$	—			$	—

Northeast G&P (2)	7,314				6,229				891				737			1,079			1,376				3,909

Atlantic-Gulf	11,124				10,007				985				930			1,593			1,072				1,002

West	4,620				4,767				—				—			168			210				360

NGL & Petchem Services	3,510				3,035				519				520			601			746				571

Other corporate assets	563				147				—				—			8			5				16

Eliminations (3)	(833		)		(614		)		—				—			—			—				—

Total	$	49,322			$	23,571			$	8,399			$	2,187		$	20,413		$	3,409			$	5,858





-1	2014 Additions to long-lived assets within our Access Midstream segment primarily includes the acquisition-date fair value of long-lived assets from the ACMP Acquisition (Note 2 – Acquisitions).


-2	2012 Additions to long-lived assets includes the Caiman and Laser Acquisitions. (See Note 2 – Acquisitions.)


-3	Eliminations primarily relate to the intercompany accounts receivable generated by our cash management program.

Subsequent_Events_Notes

Subsequent Events (Notes)	12 Months Ended
Subsequent Events (Notes)	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Note 19 – Subsequent Events
	Debt Items
	On March 3, 2015, we completed a public offering of $1.25 billion of 3.6 percent senior notes due 2022, $750 million of 4.0 percent senior notes due 2025 and $1 billion of 5.1 percent senior notes due 2045. We used the net proceeds to repay amounts outstanding under our commercial paper program and credit facility, to fund capital expenditures, and for general partnership purposes.
	On April 15, 2015, we paid $783 million, including a redemption premium, to retire $750 million of 5.875 percent senior notes due 2021.
	At May 4, 2015, we had $536 million outstanding under our commercial paper program.
	We had no outstanding borrowings under our long-term credit facility at May 4, 2015.
	Distributions
	The Board of Directors of our general partner declared a cash distribution of $0.85 per common unit on April 20, 2015 to be paid on May 14, 2015, to unitholders of record at the close of business on May 7, 2015.
	Acquisition
	On April 6, 2015, we announced our agreement to acquire an additional 21 percent equity interest in UEOM for $575 million, subject to the right of the other member of UEOM to participate in the transaction. If the other member exercises this right, we would acquire an approximate 13 percent interest and the other member would acquire an approximate 8 percent interest.

General_Description_of_Busines1

General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Principles of consolidation [Policy Text Block]	Principles of consolidation
	The consolidated financial statements include the accounts of all entities that we control and our proportionate interest in the accounts of certain ventures in which we own an undivided interest. Management’s judgment is required to evaluate whether we control an entity. Key areas of that evaluation include:

	•	Determining whether an entity is a variable interest entity (VIE);


	•	Determining whether we are the primary beneficiary of a VIE, including evaluating which activities of the VIE most significantly impact its economic performance and the degree of power that we and our related parties have over those activities through our variable interests;


	•	Identifying events that require reconsideration of whether an entity is a VIE and continuously evaluating whether we are a VIE’s primary beneficiary;


	•	Evaluating whether other owners in entities that are not VIEs are able to effectively participate in significant decisions that would be expected to be made in the ordinary course of business such that we do not have the power to control such entities.
	We apply the equity method of accounting to investments in entities over which we exercise significant influence but do not control.
Common control transactions [Policy Text Block]	Common control transactions
	Entities and assets acquired from Williams and its affiliates are accounted for as common control transactions whereby the net assets acquired are combined with ours at their historical amounts. If any cash consideration transferred in such a transaction exceeds the carrying value of the net assets acquired, the excess is treated as a capital transaction with our general partner, similar to a dividend. If the carrying value of the net assets acquired exceeds any cash consideration transferred and limited partner units are also issued as consideration, then the limited partner units are recorded at an amount equal to the excess of the carrying value of the net assets acquired over any cash consideration transferred. To the extent that such transactions require prior periods to be recast, historical net equity amounts prior to the transaction date are reflected in the account of the general partner or noncontrolling interests, if applicable. Cash consideration up to the carrying value of net assets acquired is presented as an investing activity in our Consolidated Statement of Cash Flows. Cash consideration in excess of the carrying value of net assets acquired is presented as a financing activity in our Consolidated Statement of Cash Flows.
Equity Method Investment Basis Difference Policy [Policy Textblock]	Equity-method investment basis differences
	Differences between the cost of our equity-method investments and our underlying equity in the net assets of investees are accounted for as if the investees were consolidated subsidiaries. Equity earnings (losses) in the Consolidated Statement of Comprehensive Income includes our allocable share of net income (loss) of investees adjusted for any depreciation and amortization, as applicable, associated with basis differences.
Use of estimates [Policy Text Block]	Use of estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
	Significant estimates and assumptions include:

	•	Impairment assessments of investments, property, plant, and equipment, goodwill and other identifiable intangible assets;

	•	Litigation-related contingencies;

	•	Environmental remediation obligations;

	•	Depreciation and/or amortization of equity-method investment basis differences;

	•	Asset retirement obligations;

	•	Acquisition related purchase price allocations.

	These estimates are discussed further throughout these notes.
Regulatory Accounting [Policy Text Block]	Regulatory accounting
	Transco and Northwest Pipeline are regulated by the Federal Energy Regulatory Commission (FERC). Their rates, which are established by the FERC, are designed to recover the costs of providing the regulated services, and their competitive environment makes it probable that such rates can be charged and collected. Therefore, our management has determined that it is appropriate to account for and report regulatory assets and liabilities related to these operations consistent with the economic effect of the way in which their rates are established. Accounting for these operations that are regulated can differ from the accounting requirements for nonregulated operations. The components of our regulatory assets and liabilities relate to the effects of deferred taxes on equity funds used during construction, asset retirement obligations, fuel cost differentials, levelized incremental depreciation, negative salvage, and postretirement benefits. Our current and noncurrent regulatory asset and liability balances for the years ended December 31, 2014 and 2013 are as follows:


		December 31,

		2014		2013

		(Millions)

	Current assets reported within Other current assets	$	81	$	39

	Noncurrent assets reported within Regulatory assets, deferred charges, and other	289		315

	Total regulated assets	$	370	$	354



	Current liabilities reported within Other accrued liabilities	$	11	$	19

	Noncurrent liabilities reported within Regulatory liabilities, deferred income, and other	349		289

	Total regulated liabilities	$	360	$	308



Cash and cash equivalents [Policy Text Block]	Cash and cash equivalents
	Cash and cash equivalents in the Consolidated Balance Sheet includes amounts primarily invested in funds with high-quality, short-term securities and instruments that are issued or guaranteed by the U.S. government. These have maturity dates of three months or less when acquired.
Accounts receivable [Policy Text Block]	Accounts receivable
	Accounts receivable are carried on a gross basis, with no discounting, less an allowance for doubtful accounts. We estimate the allowance for doubtful accounts based on existing economic conditions, the financial condition of our customers, and the amount and age of past due accounts. We consider receivables past due if full payment is not received by the contractual due date. Interest income related to past due accounts receivable is generally recognized at the time full payment is received or collectability is assured. Past due accounts are generally written off against the allowance for doubtful accounts only after all collection attempts have been exhausted.
Inventory valuation [Policy Text Block]	Inventory valuation
	All Inventories in the Consolidated Balance Sheet are stated at the lower of cost or market. The cost of inventories is primarily determined using the average-cost method.
Property, plant, and equipment [Policy Text Block]	Property, plant, and equipment
	Property, plant, and equipment is recorded at cost. We base the carrying value of these assets on estimates, assumptions, and judgments relative to capitalized costs, useful lives, and salvage values.
	As regulated entities, Northwest Pipeline and Transco provide for depreciation using the straight-line method at FERC-prescribed rates. Depreciation for nonregulated entities is provided primarily on the straight-line method over estimated useful lives, except for certain offshore facilities that apply an accelerated depreciation method. (See Note 11 – Property, Plant and Equipment.)
	Gains or losses from the ordinary sale or retirement of property, plant, and equipment for regulated pipelines are credited or charged to accumulated depreciation; other gains or losses are recorded in Other (income) expense – net included in Operating income in the Consolidated Statement of Comprehensive Income.
	Ordinary maintenance and repair costs are generally expensed as incurred. Costs of major renewals and replacements are capitalized as property, plant, and equipment.
	We record a liability and increase the basis in the underlying asset for the present value of each expected future asset retirement obligation (ARO) at the time the liability is initially incurred, typically when the asset is acquired or constructed. As regulated entities, Northwest Pipeline and Transco offset the depreciation of the underlying asset that is attributable to capitalized ARO cost to a regulatory asset. We measure changes in the liability due to passage of time by applying an interest rate to the liability balance. This amount is recognized as an increase in the carrying amount of the liability and as a corresponding accretion expense included in Operating and maintenance expenses in the Consolidated Statement of Comprehensive Income, except for regulated entities, for which the liability is offset by a regulatory asset as management expects to recover amounts in future rates. The regulatory asset is amortized commensurate with the collection of those costs in rates.
	Measurements of AROs include, as a component of future expected costs, an estimate of the price that a third party would demand, and could expect to receive, for bearing the uncertainties inherent in the obligations, sometimes referred to as a market-risk premium.
Goodwill [Policy Text Block]	Goodwill
	Goodwill in the Consolidated Balance Sheet represents the excess of the consideration, plus the fair value of any noncontrolling interest or any previously held equity interest, over the fair value of the net assets acquired. It is not subject to amortization but is evaluated annually as of October 1 for impairment or more frequently if impairment indicators are present that would indicate it is more likely than not that the fair value of the reporting unit is less than its carrying amount. As part of the evaluation, we compare our estimate of the fair value of the reporting unit with its carrying value, including goodwill. If the carrying value of the reporting unit exceeds its fair value, a computation of the implied fair value of the goodwill is compared with its related carrying value. If the carrying value of the reporting unit goodwill exceeds the implied fair value of that goodwill, an impairment loss is recognized in the amount of the excess.
Other intangible assets [Policy Text Block]	Other intangible assets
	Our identifiable intangible assets are primarily related to gas gathering, processing, and fractionation contractual customer relationships. Our intangible assets are amortized on a straight-line basis over the period in which these assets contribute to our cash flows. We evaluate these assets for changes in the expected remaining useful lives and would reflect any changes prospectively through amortization over the revised remaining useful life.
Impairment of property, plant, and equipment, other identifiable intangible assets and investments [Policy Text Block]	Impairment of property, plant, and equipment, other identifiable intangible assets, and investments
	We evaluate our property, plant, and equipment and other identifiable intangible assets for impairment when events or changes in circumstances indicate, in our management’s judgment, that the carrying value of such assets may not be recoverable. When an indicator of impairment has occurred, we compare our management’s estimate of undiscounted future cash flows attributable to the assets to the carrying value of the assets to determine whether an impairment has occurred and we may apply a probability-weighted approach to consider the likelihood of different cash flow assumptions and possible outcomes including selling in the near term or holding for the remaining estimated useful life. If an impairment of the carrying value has occurred, we determine the amount of the impairment recognized in the financial statements by estimating the fair value of the assets and recording a loss for the amount that the carrying value exceeds the estimated fair value. This evaluation is performed at the lowest level for which separately identifiable cash flows exist.
	For assets identified to be disposed of in the future and considered held for sale, we compare the carrying value to the estimated fair value less the cost to sell to determine if recognition of an impairment is required. Until the assets are disposed of, the estimated fair value, which includes estimated cash flows from operations until the assumed date of sale, is recalculated when related events or circumstances change.
	We evaluate our investments for impairment when events or changes in circumstances indicate, in our management’s judgment, that the carrying value of such investments may have experienced an other-than-temporary decline in value. When evidence of loss in value has occurred, we compare our estimate of fair value of the investment to the carrying value of the investment to determine whether an impairment has occurred. If the estimated fair value is less than the carrying value and we consider the decline in value to be other-than-temporary, the excess of the carrying value over the fair value is recognized in the consolidated financial statements as an impairment charge.
	Judgments and assumptions are inherent in our management’s estimate of undiscounted future cash flows and an asset’s or investment’s fair value. Additionally, judgment is used to determine the probability of sale with respect to assets considered for disposal.
Contingent liabilities [Policy Text Block]	Contingent liabilities
	We record liabilities for estimated loss contingencies, including environmental matters, when we assess that a loss is probable and the amount of the loss can be reasonably estimated. These liabilities are calculated based upon our assumptions and estimates with respect to the likelihood or amount of loss and upon advice of legal counsel, engineers, or other third parties regarding the probable outcomes of the matters. These calculations are made without consideration of any potential recovery from third parties. We recognize insurance recoveries or reimbursements from others when realizable. Revisions to these liabilities are generally reflected in income when new or different facts or information become known or circumstances change that affect the previous assumptions or estimates.
Cash flows from revolving credit facilities and commercial paper program [Policy Text Block]	Cash flows from revolving credit facility and commercial paper program
	Proceeds and payments related to borrowings under our credit facility are reflected in the financing activities in the Consolidated Statement of Cash Flows on a gross basis. Proceeds and payments related to borrowings under our commercial paper program are reflected in the financing activities in the Consolidated Statement of Cash Flows on a net basis, as the outstanding notes generally have maturity dates less than three months from the date of issuance. (See Note 13 – Debt, Banking Arrangements, and Leases.)
Derivative instruments and hedging activities [Policy Text Block]	Derivative instruments and hedging activities
	We may utilize derivatives to manage a portion of our commodity price risk. These instruments consist primarily of swaps, futures, and forward contracts involving short- and long-term purchases and sales of physical energy commodities. We report the fair value of derivatives, except those for which the normal purchases and normal sales exception has been elected, in Other current assets; Regulatory assets, deferred charges, and other; Other accrued liabilities; or Regulatory liabilities, deferred income, and other in the Consolidated Balance Sheet. We determine the current and noncurrent classification based on the timing of expected future cash flows of individual trades. We report these amounts on a gross basis. Additionally, we report cash collateral receivables and payables with our counterparties on a gross basis. (See Note 16 – Fair Value Measurements, Guarantees, and Concentration of Credit Risk.)
	The accounting for the changes in fair value of a commodity derivative can be summarized as follows:


	Derivative Treatment		Accounting Method
	Normal purchases and normal sales exception		Accrual accounting
	Designated in a qualifying hedging relationship		Hedge accounting
	All other derivatives		Mark-to-market accounting
	We may elect the normal purchases and normal sales exception for certain short- and long-term purchases and sales of physical energy commodities. Under accrual accounting, any change in the fair value of these derivatives is not reflected on the balance sheet after the initial election of the exception.
	We may also designate a hedging relationship for certain commodity derivatives. For a derivative to qualify for designation in a hedging relationship, it must meet specific criteria and we must maintain appropriate documentation. We establish hedging relationships pursuant to our risk management policies. We evaluate the hedging relationships at the inception of the hedge and on an ongoing basis to determine whether the hedging relationship is, and is expected to remain, highly effective in achieving offsetting changes in fair value or cash flows attributable to the underlying risk being hedged. We also regularly assess whether the hedged forecasted transaction is probable of occurring. If a derivative ceases to be or is no longer expected to be highly effective, or if we believe the likelihood of occurrence of the hedged forecasted transaction is no longer probable, hedge accounting is discontinued prospectively, and future changes in the fair value of the derivative are recognized currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income.
	For commodity derivatives designated as a cash flow hedge, the effective portion of the change in fair value of the derivative is reported in Accumulated other comprehensive income (loss) (AOCI) in the Consolidated Balance Sheet and reclassified into earnings in the period in which the hedged item affects earnings. Any ineffective portion of the derivative’s change in fair value is recognized currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income. Gains or losses deferred in AOCI associated with terminated derivatives, derivatives that cease to be highly effective hedges, derivatives for which the forecasted transaction is reasonably possible but no longer probable of occurring, and cash flow hedges that have been otherwise discontinued remain in AOCI until the hedged item affects earnings. If it becomes probable that the forecasted transaction designated as the hedged item in a cash flow hedge will not occur, any gain or loss deferred in AOCI is recognized in Product sales or Product costs in the Consolidated Statement of Comprehensive Income at that time. The change in likelihood of a forecasted transaction is a judgmental decision that includes qualitative assessments made by management.
	For commodity derivatives that are not designated in a hedging relationship, and for which we have not elected the normal purchases and normal sales exception, we report changes in fair value currently in Product sales or Product costs in the Consolidated Statement of Comprehensive Income.
	Certain gains and losses on derivative instruments included in the Consolidated Statement of Comprehensive Income are netted together to a single net gain or loss, while other gains and losses are reported on a gross basis. Gains and losses recorded on a net basis include unrealized gains and losses on all derivatives that are not designated as hedges and for which we have not elected the normal purchases and normal sales exception.
	Realized gains and losses on derivatives that require physical delivery, as well as natural gas derivatives for NGL processing activities and which are not held for trading purposes nor were entered into as a pre-contemplated buy/sell arrangement, are recorded on a gross basis.
Revenues [Policy Text Block]	Revenues
	As a result of the ratemaking process, certain revenues collected by us may be subject to refunds upon the issuance of final orders by the FERC in pending rate proceedings. We record estimates of rate refund liabilities considering our and other third-party regulatory proceedings, advice of counsel and other risks.
	Service revenues
	Revenues include services pursuant to long-term firm transportation and storage agreements within our interstate natural gas pipeline businesses. These agreements provide for a reservation charge based on the volume of a contracted capacity and a commodity charge based on the volume of gas delivered, both at rates specified in our FERC tariffs. We recognize revenues for reservation charges ratably over the contract period regardless of the volume of natural gas that is transported or stored. Revenues for commodity charges, from both firm and interruptible transportation services, and storage injection and withdrawal services are recognized when natural gas is delivered at the agreed upon delivery point or when natural gas is injected or withdrawn from the storage facility.
	Certain revenues from our midstream operations include those derived from natural gas gathering, processing, treating, and compression services and are performed under volumetric-based fee contracts. These revenues are recorded when services have been performed.
	Certain of our gas gathering agreements have minimum volume commitments. If a customer under such an agreement fails to meet its minimum volume commitment for a specified period, generally measured on an annual basis, it is obligated to pay a contractually determined fee based upon the shortfall between actual production volumes and the minimum volume commitment for that period. The revenue associated with minimum volume commitments is recognized in the period that the actual shortfall is determined and is no longer subject to future reduction or offset.
	Crude oil gathering and transportation revenues and offshore production handling fees are recognized when the services have been performed. Certain offshore production handling contracts contain fixed payment terms that result in the deferral of revenues until such services have been performed or capacity has been provided.

	Storage revenues from our midstream operations associated with prepaid contracted storage capacity contracts are recognized on a straight-line basis over the life of the contract as services are provided.
	Product sales
	In the course of providing transportation services to customers of our interstate natural gas pipeline businesses, we may receive different quantities of gas from shippers than the quantities delivered on behalf of those shippers. The resulting imbalances are primarily settled through the purchase and sale of gas with our customers under terms provided for in our FERC tariffs. Revenue is recognized from the sale of gas upon settlement of the transportation and exchange imbalances.
	We market NGLs, crude oil, natural gas, and olefins that we purchase from our producer customers as part of the overall service provided to producers. Revenues from marketing NGLs are recognized when the products have been sold and delivered.
	Under our keep-whole and percent-of-liquids processing contracts, we retain the rights to all or a portion of the NGLs extracted from the producers’ natural gas stream and recognize revenues when the extracted NGLs are sold and delivered.
	Our domestic olefins business produces olefins from purchased or produced feedstock and we recognize revenues when the olefins are sold and delivered.
	Our Canadian business has processing and fractionation operations where we retain certain NGLs and olefins from an upgrader’s offgas stream and we recognize revenues when the fractionated products are sold and delivered.
Interest capitalized [Policy Text Block]	Interest capitalized
	We capitalize interest during construction on major projects with construction periods of at least 3 months and a total project cost in excess of $1 million. Interest is capitalized on borrowed funds and, where regulation by the FERC exists, on internally generated funds. The latter is included in Other income (expense) – net below Operating income in the Consolidated Statement of Comprehensive Income. The rates used by regulated companies are calculated in accordance with FERC rules. Rates used by nonregulated companies are based on our average interest rate on debt.
Income taxes [Policy Text Block]	Income taxes
	We generally are not a taxable entity for income tax purposes, with the exception of Texas franchise tax and foreign income taxes associated with our Canadian operations. Other income taxes are generally borne by individual partners. Net income for financial statement purposes may differ significantly from taxable income of unitholders as a result of differences between the tax basis and financial reporting basis of assets and liabilities and the taxable income allocation requirements under our partnership agreement. The aggregated difference in the basis of our net assets for financial and tax reporting purposes cannot be readily determined because information regarding each partner’s tax attributes in us is not available to us.
	Foreign deferred income taxes are computed using the liability method and are provided on all temporary differences between the financial basis and the tax basis of the related assets and liabilities. Our management’s judgment and income tax assumptions are used to determine the levels, if any, of valuation allowances associated with deferred tax assets.
Earnings per unit [Policy Text Block]	Earnings per unit
	We use the two-class method to calculate basic and diluted earnings per unit whereby net income, adjusted for items specifically allocated to our general partner, is allocated on a pro-rata basis between unitholders and our general partner. Basic and diluted earnings per unit are based on the average number of common units outstanding. Basic and diluted earnings per unit are equivalent as there are no dilutive securities outstanding.
Pension and other postretirement benefits [Policy Text Block]	Pension and other postretirement benefits
	We do not have employees. Certain of the costs charged to us by Williams associated with employees who directly support us include costs related to Williams’ pension and other postretirement benefit plans. (See Note 9 – Benefit Plans.) Although the underlying benefit plans of Williams are single-employer plans, we follow multiemployer plan accounting whereby the amount charged to us, and thus paid by us, is based on our share of net periodic benefit cost.
Foreign Currency Translation [Policy Text Block]	Foreign currency translation
	Our foreign subsidiaries use the Canadian dollar as their functional currency. Assets and liabilities of such foreign subsidiaries are translated at the spot rate in effect at the applicable reporting date, and the combined statements of comprehensive income are translated into the U.S. dollar at the average exchange rates in effect during the applicable period. The resulting cumulative translation adjustment is recorded as a separate component of AOCI.
	Transactions denominated in currencies other than the functional currency are recorded based on exchange rates at the time such transactions arise. Subsequent changes in exchange rates when the transactions are settled result in transaction gains and losses which are reflected in the Consolidated Statement of Comprehensive Income.
	Accumulated Other Comprehensive Income (Loss)
	AOCI is substantially comprised of foreign currency translation adjustments. These adjustments did not impact Net income in any of the periods presented.

General_Description_of_Busines2

General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Regulatory Assets and Liabilities [Table Text Block]	Our current and noncurrent regulatory asset and liability balances for the years ended December 31, 2014 and 2013 are as follows:


		December 31,

		2014		2013

		(Millions)

	Current assets reported within Other current assets	$	81	$	39

	Noncurrent assets reported within Regulatory assets, deferred charges, and other	289		315

	Total regulated assets	$	370	$	354



	Current liabilities reported within Other accrued liabilities	$	11	$	19

	Noncurrent liabilities reported within Regulatory liabilities, deferred income, and other	349		289

	Total regulated liabilities	$	360	$	308

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2014
Business Acquisition [Line Items]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The following table presents the preliminary allocation of the acquisition-date fair value of the major classes of the assets acquired, which are presented in the Access Midstream segment, liabilities assumed, noncontrolling interest, and equity at July 1, 2014. The allocation is considered preliminary because the valuation work has not been completed due to the ongoing review of the valuation results and validation of significant inputs and assumptions. Significant changes since the allocation disclosed in the third quarter reflect an increase in investments and decreases in goodwill, other intangible assets, and property, plant and equipment - net, generally associated with the attribution of fair value between consolidated and non-consolidated operations. The fair value of accounts receivable acquired equals contractual amounts receivable.


		(Millions)
	Accounts receivable	$	168

	Other current assets	63

	Investments	5,872

	Property, plant, and equipment – net	7,015

	Goodwill	474

	Other intangible assets	9,009

	Current liabilities	(408		)
	Debt	(4,052		)
	Other noncurrent liabilities	(9		)
	Noncontrolling interest in ACMP’s subsidiaries	(958		)
	Noncontrolling interest representing Pre-merger ACMP public unitholders	(6,544		)
	Equity	(10,630		)
Business Acquisition, Pro Forma Information [Table Text Block]	The following unaudited pro forma Revenues and Net income attributable to controlling interests for the years ended December 31, 2014 and 2013, are presented as if the ACMP Acquisition had been completed on January 1, 2013. These pro forma amounts are not necessarily indicative of what the actual results would have been if the acquisition had in fact occurred on the date or for the periods indicated, nor do they purport to project Revenues or Net income attributable to controlling interests for any future periods or as of any date. These amounts do not give effect to any potential cost savings, operating synergies, or revenue enhancements to result from the transactions or the potential costs to achieve these cost savings, operating synergies, and revenue enhancements.



			December 31,
			2014			2013
			(Millions)
	Revenues		$	7,953		$	7,881

	Net income attributable to controlling interests		$	1,376		$	1,172

LaserAndCaimanAcquisitions [Member]
Business Acquisition [Line Items]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The following table presents the allocation of the acquisition-date fair value of the major classes of the net assets, which are included in the Northeast G&P segment:


		Laser			Caiman
		(Millions)
	Assets held-for-sale	$	18		$	—

	Other current assets	3			16

	Property, plant, and equipment	158			656

	Intangible assets	318			1,393

	Current liabilities	(21		)	(94		)
	Noncurrent liabilities	—			(3		)

	Identifiable net assets acquired	476			1,968

	Goodwill	290			356

		$	766		$	2,324

Variable_Interest_Entities_Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2014
Variable Interest Entity Disclosures [Abstract]
Schedule of Variable Interest Entities [Table Text Block]	The following table presents amounts included in our Consolidated Balance Sheet that are for the use or obligation of our consolidated VIEs.


		December 31,
		2014			2013			Classification
		(Millions)
	Assets (liabilities):
	Cash and cash equivalents	$	113		$	84		Cash and cash equivalents

	Accounts receivable	52			—			Trade accounts and notes receivable, net

	Other current assets	3			—			Other current assets

	Property, plant, and equipment - net	2,794			1,001			Property, plant, and equipment – net

	Goodwill	103			—			Goodwill

	Other intangible assets, net	1,493			—			Other intangible assets – net of accumulated amortization

	Other noncurrent assets	14			—			Regulatory assets, deferred charges, and other

	Accounts payable	(48		)	(122		)	Accounts payable - trade
	Accrued liabilities	(36		)	(3		)	Other accrued liabilities
	Current deferred revenue	(45		)	(10		)	Other accrued liabilities
	Noncurrent deferred income taxes	(13		)	—			Deferred income taxes

	Asset retirement obligation	(94		)	—			Asset retirement obligations, noncurrent

	Noncurrent deferred revenue associated with customer advance payments	(395		)	(115		)	Regulatory liabilities, deferred income and other

Allocation_of_Net_Income_and_D1

Allocation of Net Income and Distributions (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Allocation of net income among our general partner, limited partners, and noncontrolling interests	The allocation of net income among our general partner, limited partners, and noncontrolling interests as reflected in the Consolidated Statement of Changes in Equity is as follows:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Allocation of net income to general partner:
	Net income	$	1,284		$	1,119		$	1,291

	Net income applicable to pre-merger operations allocated to general partner	(95		)	—			—

	Net income applicable to pre-partnership operations allocated to general partner	(15		)	(49		)	(244		)
	Net income applicable to noncontrolling interests	(96		)	(3		)	—

	Costs charged directly to general partner	1			1			1

	Income subject to 2% allocation of general partner interest	1,079			1,068			1,048

	General partner’s share of net income	2		%	2		%	2		%
	General partner’s allocated share of net income before items directly allocable to general partner interest	22			21			21

	Priority allocations, including incentive distributions, paid to general partner	641			387			355

	Costs charged directly to general partner	(1		)	(1		)	(1		)
	Pre-merger net income allocated to general partner interest	95			—			—

	Pre-partnership net income allocated to general partner interest	15			49			244

	Net income allocated to general partner	$	772		$	456		$	619

	Net income	$	1,284		$	1,119		$	1,291

	Net income allocated to general partner’s equity	772			456			619

	Net income allocated to Class D limited partners’ equity (1)	62			—			—

	Net income allocated to noncontrolling interests	96			3			—

	Net income allocated to common limited partners’ equity	$	354		$	660		$	672


	Adjustments to reconcile Net income allocated to common limited partners' equity
	to Allocation of net income to common units:
	Incentive distributions paid	640			383			355

	Incentive distributions declared (2)	(626		)	(432		)	(382		)
	Impact of Class D issuance timing	(9		)	—			—

	Allocation of net income to common units	$	359		$	611		$	645


	____________

	-1	The net income allocated to Pre-merger WPZ Class D limited partners includes $49 million for the year ended December 31, 2014, related to the amortization of the beneficial conversion feature associated with the Pre-merger WPZ Class D units.

	-2	Following the completion of the Merger, we paid a cash distribution of $0.85 per unit on February 13, 2015, on our outstanding common units to unitholders of record at the close of business on February 9, 2015. For the purpose of determining the Allocation of net income to common units for the calculation of earnings per unit, the incentive distribution declared for the fourth quarter of 2014 reflects only the portion of the total incentive distribution associated with the Pre-merger WPZ common units exchanged in the Merger.

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	Summary of the related party transactions discussed in all sections above.


		Years Ended December 31,
		2014		2013		2012
		(Millions)
	Service revenues	$	13	$	—	$	—

	Product costs	186		147		171

	Operating and maintenance expenses - employee costs	413		339		275

	Selling, general, and administrative expenses:
	Employee direct costs	331		270		308

	Employee allocated costs	171		169		190

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Investments [Table Text Block]	Investments accounted for using the equity method consist of:


		December 31,
		2014			2013
		(Millions)
	Appalachia Midstream Investments (2)	$	3,033		$	—

	Delaware Basin gas gathering system – 50% (2)	1,478			—

	UEOM – 49% (2)	1,411			—

	Discovery – 60% (1)	602			527

	Laurel Mountain – 69% (1)	459			481

	OPPL – 50%	453			452

	Caiman II – 58% (1)	432			256

	Gulfstream – 50%	317			333

	Other	214			138

		$	8,399		$	2,187

	____________

	-1	We account for these investments under the equity method due to the significant participatory rights of our partners such that we do not control or are otherwise not the primary beneficiary of the investments.

	-2	These are Pre-merger ACMP investments. The Appalachia Midstream Investments include investments in 11 different gathering systems in the Marcellus Shale. Ownership interests range from 33.75 percent to 67.50 percent, resulting in an overall approximate average interest of 45 percent. For those investments where we own in excess of 50 percent, we apply the equity-method of accounting due to the significant participation rights of our partners such that we do not control. (See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.)
Contributions [Table Text Block]

		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Caiman II	$	175		$	192		$	69

	Discovery	106			193			169

	Appalachia Midstream Investments	84			—			—

	UEOM	57			—			—

	Delaware Basin gas gathering system	20			—			—

	Laurel Mountain	12			42			174

Dividends and distributions [Table Text Block]

		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Appalachia Midstream Investments	$	120		$	—		$	—

	Gulfstream	81			81			78

	Laurel Mountain	39			—			—

	Discovery	36			12			21

	OPPL	27			27			28

	Aux Sable Liquid Products L.P.	15			20			28

Summarized Financial Position and Results of Operations of Equity Method Investments [Table Text Block]	Summarized Financial Position and Results of Operations of All Equity-Method Investments


		December 31,
		2014			2013
		(Millions)
	Assets (liabilities):
	Current assets	$	599		$	412

	Noncurrent assets	9,135			5,956

	Current liabilities	(850		)	(264		)
	Noncurrent liabilities	(954		)	(1,305		)



		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Gross revenue	$	1,623		$	1,333		$	1,213

	Operating income	534			367			378

	Net income	460			291			309

Other_Income_and_Expenses_Tabl

Other Income and Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Other Income and Expenses [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	The following table presents certain gains or losses reflected in Other (income) expense – net within Costs and expenses in our Consolidated Statement of Comprehensive Income:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Access Midstream
	Loss related to sale of certain assets	$	10		$	—		$	—

	Impairment of certain materials and equipment held for sale (See Note 16)	12			—			—

	Northeast G&P
	Contingency gain settlement	(154		)	—			—

	Impairment of certain materials and equipment (See Note 16)	30			—			—

	Net gain related to partial acreage dedication release	(12		)	—			—

	Loss associated with a producer claim	—			25			—

	Atlantic-Gulf
	Amortization of regulatory assets associated with asset retirement obligations	33			30			7

	Impairment of certain equipment	10			—			—

	Write-off of the Eminence abandonment regulatory asset not recoverable through rates	(3		)	12			—

	Insurance recoveries associated with the Eminence abandonment	—			(16		)	—

	Project feasibility costs	2			4			21

	Capitalization of project feasibility costs previously expensed	(5		)	(1		)	(19		)

Provision_Benefit_for_Income_T1

Provision (Benefit) for Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The Provision (benefit) for income taxes includes:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Current:
	State	$	3		$	2		$	11

	Foreign	1			(22		)	26

		4			(20		)	37

	Deferred:
	State	8			15			—

	Foreign	17			35			5

		25			50			5

	Total provision (benefit)	$	29		$	30		$	42

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Reconciliations from the Provision (benefit) for income taxes at the federal statutory rate to the recorded Provision (benefit) for income taxes are as follows:


		Years Ended December 31,
		2014			2013			2012
		(Millions)
	Provision at statutory rate	$	462		$	402		$	467

	Increases (decreases) in taxes resulting from:
	Income not subject to U.S. federal tax	(462		)	(402		)	(467		)
	State income taxes	11			17			11

	Foreign operations — net	18			13			31

	Provision (benefit) for income taxes	$	29		$	30		$	42

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories [Table Text Block]

		December 31,

		2014		2013

		(Millions)

	Natural gas liquids, olefins, and natural gas in underground storage	$	150	$	111

	Materials, supplies, and other	81		83

		$	231	$	194

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Propertyl, Plant, and Equipment [Table Text Block]

		Estimated		Depreciation
		Useful Life (1)		Rates (1)	December 31,
		(Years)		(%)	2014			2013
					(Millions)
	Nonregulated:
	Natural gas gathering and processing facilities	5 - 40			$	18,717		$	9,172

	Construction in progress	Not applicable			2,115			2,727

	Other	3 - 45			1,459			964

	Regulated:
	Natural gas transmission facilities			1.2 - 6.97	10,867			10,633

	Construction in progress			Not applicable	985			273

	Other			1.35 - 33.33	1,336			1,293

	Total property, plant, and equipment, at cost				$	35,479		$	25,062

	Accumulated depreciation and amortization				(8,157		)	(7,437		)
	Property, plant, and equipment – net				$	27,322		$	17,625

	____________

	-1	Estimated useful life and depreciation rates are presented as of December 31, 2014. Depreciation rates for regulated assets are prescribed by the FERC.
Asset Retirement Obligation [Table Text Block]

		December 31,
		2014			2013
		(Millions)
	Beginning balance	$	561		$	579

	Liabilities incurred	101			8

	Liabilities settled (1)	(21		)	(31		)
	Accretion expense	44			53

	Revisions (2)	146			(48		)

	Ending balance	$	831		$	561

	______________

	-1	For 2014 and 2013, liabilities settled include $7 million and $25 million, respectively, related to the abandonment of certain of Transco’s natural gas storage caverns that are associated with a leak in 2010.


	-2	Several factors are considered in the annual review process, including inflation rates, current estimates for removal cost, discount rates, and the estimated remaining life of the assets. The 2014 revisions primarily reflect an increase in the estimated retirement costs for our offshore pipelines, an increase in the inflation rate and decreases in the discount rates used in the annual review process. The 2013 revision primarily reflects increases in the estimated remaining useful life of the assets. The 2013 revision also includes an increase of $9 million related to changes in the timing and method of abandonment on certain of Transco’s natural gas storage caverns that were associated with a leak in 2010.

Goodwill_and_Other_Intangible_1

Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill [Table Text Block]	Changes in the carrying amount of goodwill by reportable segment for the periods indicated are as follows:


		Access Midstream		Northeast G&P			Total
		(Millions)
	31-Dec-13	$	—	$	646		$	646

	Acquisition	474		—			474

	31-Dec-14	$	474	$	646		$	1,120

Schedule of Finite-Lived Intangible Assets [Table Text Block]	The gross carrying amount and accumulated amortization of Other intangible assets – net of accumulated amortization at December 31 are as follows:


		2014					2013
		Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
		(Millions)
	Contractual customer relationships	$	10,761	$	(310	)	$	1,747	$	(105	)

Debt_Banking_Arrangements_and_1

Debt, Banking Arrangements, and Leases (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table Text Block]	Long-Term Debt


			December 31,
			2014			2013
			(Millions)
	Unsecured:
	Transco:
	6.4% Notes due 2016		$	200		$	200

	6.05% Notes due 2018		250			250

	7.08% Debentures due 2026		8			8

	7.25% Debentures due 2026		200			200

	5.4% Notes due 2041		375			375

	4.45% Notes due 2042		400			400

	Northwest Pipeline:
	7% Notes due 2016		175			175

	5.95% Notes due 2017		185			185

	6.05% Notes due 2018		250			250

	7.125% Debentures due 2025		85			85

	Williams Partners L.P.:
	3.8% Notes due 2015 (3)		750			750

	7.25% Notes due 2017		600			600

	5.25% Notes due 2020		1,500			1,500

	4.125% Notes due 2020		600			600

	5.875% Notes due 2021 (1)		750			—

	4% Notes due 2021		500			500

	3.35% Notes due 2022		750			750

	6.125% Notes due 2022 (1)		750			—

	4.875% Notes due 2023 (1)		1,400			—

	4.5% Notes due 2023		600			600

	4.3% Notes due 2024		1,000			—

	4.875% Notes due 2024 (1)		750			—

	3.9% Notes due 2025		750			—

	6.3% Notes due 2040		1,250			1,250

	5.8% Notes due 2043		400			400

	5.4% Notes due 2044		500			—

	4.9% Notes due 2045		500			—

Pre-merger ACMP Credit facility loans (1)		640			—

Capital lease obligations		5			—

Net unamortized debt premium (discount) (2)		207			(21		)

Long-term debt, including current portion		16,330			9,057

Long-term debt due within one year		(4		)	—

Long-term debt		$	16,326		$	9,057

______________________________________________________
(1) These notes and credit facility loans are associated with Pre-merger ACMP. See Note 1 – General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies and Note 2 – Acquisitions.
(2) Includes premium related to the fair value of Pre-merger ACMP debt. See Note 2 – Acquisitions.

-3	Presented as long-term debt due to our intent and ability to refinance.
Schedule of Maturities of Long-term Debt [Table Text Block]	The following table presents aggregate minimum maturities of long-term debt, excluding net unamortized debt premium (discount) and capital lease obligations, for each of the next five years:


		December 31,
		2014
		(Millions)
	2015	$	—

	2016	375

	2017	785

	2018	1,140

	2019	—

Schedule of Line of Credit Facilities [Table Text Block]	Credit Facilities


		31-Dec-14
		Available			Outstanding
		(Millions)
	Pre-merger WPZ credit facility (1)(3)
	Loans	$	2,500		$	—

	Letters of credit sub-limit	1,300			—

	Letters of credit under certain bilateral bank agreements				1

	Pre-merger ACMP credit facility (2)
	Loans	1,750			640

	Letters of credit sub-limit	200			2

	Swing line advances sub-limit	100			—

	________________

	-1	Under certain conditions, the amount available may be increased up to an additional $500 million.

	-2	Under certain conditions, the amount available may be increased up to an additional $250 million.

	-3	Transco and Northwest Pipeline are each able to borrow up to $500 million under this credit facility to the extent not otherwise utilized by the other co-borrowers.
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	The future minimum annual rentals under noncancelable operating leases, are payable as follows:


		December 31,
		2014
		(Millions)
	2015	$	72

	2016	62

	2017	49

	2018	37

	2019	33

	Thereafter	129

	Total	$	382

Partners_Capital_Tables

Partners' Capital (Tables)	12 Months Ended
Partners' Capital (Tables)	Dec. 31, 2014
Partners' Capital Notes [Abstract]
Incentive Distribution Percentage By Specified Target Level [Table Text Block]	Incentive Distribution Rights
	Our general partner is entitled to incentive distributions if the amount we distribute to unitholders with respect to any quarter exceeds specified target levels shown below:


		Total Quarterly Distribution per unit (1)	Unitholders (1)	General
		Total Quarterly Distribution per unit (1)	Unitholders (1)	Partner (1)
	Minimum Quarterly Distribution	$0.34	98%	2%
	First Target Distribution	Up to $0.388125	98	2
	Second Target Distribution	Above $0.388125 up to $0.421875	85	15
	Third Target Distribution	Above $0.421875 up to $0.50625	75	25
	Thereafter	Above $0.50625	50	50

EquityBased_Compensation_Table

Equity-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]	The following summary reflects nonvested restricted stock unit activity for awards issued by Pre-merger ACMP and related information for the six months ended December 31, 2014:


	Restricted Stock Units Outstanding	Units	Weighted-
			Average
			Fair Value
		(Millions)
	Granted	1.3	$	59.67

	Forfeited	—	$	63.89

	Vested	—	$	63.75

	Nonvested at December 31, 2014	1.3	$	59.35

Fair_Value_Measurements_Guaran1

Fair Value Measurements Guarantees and Concentration of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

								Fair Value Measurements Using
		Carrying			Fair			Quoted		Significant			Significant
		Amount			Value			Prices In		Other			Unobservable
								Active		Observable			Inputs
								Markets for		Inputs			(Level 3)
								Identical		(Level 2)
								Assets
								(Level 1)
		(Millions)
	Assets (liabilities) at December 31, 2014:
	Measured on a recurring basis:
	ARO Trust investments	$	48		$	48		$	48	$	—		$	—

	Energy derivatives assets not designated as hedging instruments	3			3			1		—			2

	Energy derivatives liabilities not designated as hedging instruments	(2		)	(2		)	—		—			(2		)

	Additional disclosures:
	Notes receivable and other	5			4			—		4			—

	Long-term debt, including current portion (1)	(16,325		)	(16,607		)	—		(16,607		)	—

	Assets (liabilities) at December 31, 2013:
	Measured on a recurring basis:
	ARO Trust investments	$	33		$	33		$	33	$	—		$	—

	Energy derivatives assets not designated as hedging instruments	3			3			—		—			3

	Energy derivatives liabilities not designated as hedging instruments	(3		)	(3		)	—		(1		)	(2		)

	Additional disclosures:
	Notes receivable and other	7			7			1		6			—

	Long-term debt, including current portion	(9,057		)	(9,581		)	—		(9,581		)	—

Concentration of receivables, net of allowances, by product or service [Table Text Block]	The following table summarizes concentration of receivables, net of allowances.


		December 31,
		2014			2013
		(Millions)
	NGLs, natural gas, and related products and services	$	728		$	341

	Transportation of natural gas and related products	175			193

	Other	2			34

	Total	$	905		$	568

Segment_Disclosures_Tables

Segment Disclosures (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	The following geographic area data includes Revenues from external customers based on product shipment origin and Long-lived assets based upon physical location.


				United States				Canada				Total
				(Millions)
	Revenues from external customers:
		2014		$	7,212			$	197			$	7,409

		2013		6,685				150				6,835

		2012		7,320				151				7,471


	Long-lived assets:
		2014		$	37,798			$	1,095			$	38,893

		2013		18,776				1,137				19,913

		2012		16,637				870				17,507

	Long-lived assets are comprised of property, plant, and equipment, goodwill, and other intangible assets.
Reconciliation of segment revenues and segment profit (loss) [Table Text Block]	The following table reflects the reconciliation of Segment revenues and Segment profit (loss) to Total revenues and Operating income as reported in the Consolidated Statement of Comprehensive Income. It also presents other financial information related to long-lived assets.


		Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
						G&P				Gulf							Petchem
																	Services
		(Millions)

	2014
	Segment revenues:

	Service revenues

	External	$	781			$	450			$	1,497			$	1,034		$	126		$	—			$	3,888

	Internal	—				1				4				—			—			(5		)		—

	Total service revenues	781				451				1,501				1,034			126			(5		)		3,888

	Product sales
	External	—				225				499				70			2,727			—				3,521

	Internal	—				5				354				476			259			(1,094		)		—

	Total product sales	—				230				853				546			2,986			(1,094		)		3,521

	Total revenues	$	781			$	681			$	2,354			$	1,580		$	3,112		$	(1,099	)		$	7,409

	Segment profit (loss)	$	265			$	212			$	635			$	631		$	265						$	2,008

	Less equity earnings (losses)	96				19				76				—			37							228

	Segment operating income (loss)	$	169			$	193			$	559			$	631		$	228						1,780

	General corporate expenses																							(171		)
	Operating income																							$	1,609


	Other financial information:
	Depreciation and amortization	$	296			$	170			$	379			$	239		$	67						$	1,151


	2013
	Segment revenues:
	Service revenues
	External	$	—			$	335			$	1,414			$	1,053		$	112		$	—			$	2,914

	Internal	—				—				10				1			—			(11		)		—

	Total service revenues	—				335				1,424				1,054			112			(11		)		2,914

	Product sales
	External	—				166				830				64			2,861			—				3,921

	Internal	—				—				95				708			294			(1,097		)		—

	Total product sales	—				166				925				772			3,155			(1,097		)		3,921

	Total revenues	$	—			$	501			$	2,349			$	1,826		$	3,267		$	(1,108	)		$	6,835

	Segment profit (loss)	$	—			$	(24	)		$	614			$	741		$	346						$	1,677

	Less:
	Equity earnings (losses)	—				(7		)		72				—			39							104

Income (loss) from investments	—				—				—				—			(3		)					(3		)

Segment operating income (loss)	$	—			$	(17	)		$	542			$	741		$	310						1,576

General corporate expenses																							(169		)
Operating income																							$	1,407


Other financial information:
Depreciation and amortization	$	—			$	132			$	363			$	236		$	60						$	791




	Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
					G&P				Gulf							Petchem
																Services
	(Millions)

2012
Segment revenues:
Service revenues
External	$	—			$	168			$	1,371			$	1,067		$	108		$	—			$	2,714

Internal	—				—				12				5			—			(17		)		—

Total service revenues	—				168				1,383				1,072			108			(17		)		2,714

Product sales
External	—				2				709				40			4,006			—				4,757

Internal	—				—				363				1,089			258			(1,710		)		—

Total product sales	—				2				1,072				1,129			4,264			(1,710		)		4,757

Total revenues	$	—			$	170			$	2,455			$	2,201		$	4,372		$	(1,727	)		$	7,471

Segment profit (loss)	$	—			$	(37	)		$	574			$	980		$	390						$	1,907

Less:
Equity earnings (losses)	—				(23		)		92				—			42							111

Income (loss) from investments	—				—				—				—			(4		)					(4		)

Segment operating income (loss)	$	—			$	(14	)		$	482			$	980		$	352						1,800

General corporate expenses																							(190		)
Operating income																							$	1,610


Other financial information:
Depreciation and amortization	$	—			$	76			$	381			$	234		$	43						$	734

Revenue from External Customers by Services [Table Text Block]	Revenues by service that exceeded 10 percent of consolidated revenue include:


		Access Midstream				Northeast				Atlantic-				West			NGL &			Eliminations				Total
						G&P				Gulf							Petchem
																	Services
		(Millions)
	2014
	Service:
	Regulated natural gas transportation and storage	$	—			$	—			$	1,313			$	470		$	—		$	(2	)		$	1,781

	Gathering & processing	781				394				79				544			—			(2		)		1,796


	2013
	Service:
	Regulated natural gas transportation and storage	$	—			$	—			$	1,244			$	469		$	—		$	(9	)		$	1,704

	Gathering & processing	—				302				70				562			—			(2		)		932


	2012
	Service:
	Regulated natural gas transportation and storage	$	—			$	—			$	1,171			$	438		$	—		$	(11	)		$	1,598

	Gathering & processing	—				159				80				607			—			(2		)		844

Total assets and investments by reporting segment [Table Text Block]	The following table reflects Total assets, Investments, and Additions to long-lived assets by reportable segments:


		Total Assets at December 31,								Investments at December 31,							Additions to Long-Lived Assets at December 31,
		2014				2013				2014				2013			2014			2013				2012
		(Millions)
	Access Midstream (1)	$	23,024			$	—			$	6,004			$	—		$	16,964		$	—			$	—

	Northeast G&P (2)	7,314				6,229				891				737			1,079			1,376				3,909

	Atlantic-Gulf	11,124				10,007				985				930			1,593			1,072				1,002

	West	4,620				4,767				—				—			168			210				360

	NGL & Petchem Services	3,510				3,035				519				520			601			746				571

	Other corporate assets	563				147				—				—			8			5				16

	Eliminations (3)	(833		)		(614		)		—				—			—			—				—

	Total	$	49,322			$	23,571			$	8,399			$	2,187		$	20,413		$	3,409			$	5,858





	-1	2014 Additions to long-lived assets within our Access Midstream segment primarily includes the acquisition-date fair value of long-lived assets from the ACMP Acquisition (Note 2 – Acquisitions).


	-2	2012 Additions to long-lived assets includes the Caiman and Laser Acquisitions. (See Note 2 – Acquisitions.)


	-3	Eliminations primarily relate to the intercompany accounts receivable generated by our cash management program.

General_Description_of_Busines3

General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended			1 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2014	Feb. 28, 2014	Jun. 30, 2014	Nov. 30, 2012	Mar. 31, 2013	Feb. 02, 2015	Jul. 01, 2014	Dec. 20, 2012
Description Of Business [Abstract]
Parent, general partner ownership percentage	2.00%	2.00%	2.00%
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Net Income (Loss) Allocated to General Partners	$756,000,000	$505,000,000	$646,000,000
Other Comprehensive Income (Loss), Net of Tax	-90,000,000	-55,000,000	20,000,000
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets, Current	81,000,000	39,000,000
Regulatory Assets, Noncurrent	289,000,000	315,000,000
Total regulatory asset	370,000,000	354,000,000
Regulatory Liability, Current	11,000,000	19,000,000
Regulatory Liability, Noncurrent	349,000,000	289,000,000
Total regulatory liabilities	360,000,000	308,000,000
Minimum period of construction for capitalization of interest	3 months
Minimum total project cost for capitalization of interest	1,000,000
General Partner [Member]
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Other Comprehensive Income (Loss), Net of Tax	0	0	0
Access Midstream Partners Acquisition [Member] \| General Partner [Member]
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired										50.00%	50.00%
Canada Acquisition [Member]
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Net Income (Loss) Allocated to General Partners		49,000,000	59,000,000
Payments to Acquire Businesses, Gross	56,000,000					31,000,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares					25,577,521
Proceeds from Previous Acquisition				56,000,000
Reduction in incentive distribution rights payment				2,000,000
Other Comprehensive Income (Loss), Net of Tax		-56,000,000	20,000,000
Geismar Acquisition [Member]
Business Acquisition, Entity Acquired and Reason for Acquisition [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired							83.30%
Payments to Acquire Businesses, Gross							25,000,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares							42,778,812
Proceeds from Previous Acquisition								25,000,000
Reduction in incentive distribution rights payment								4,000,000
Gulfstream Natural Gas System, L.L.C. [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Laurel Mountain Midstream, LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	69.00%
Discovery Producer Services LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	60.00%
Overland Pass Pipeline Company LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Utica East Ohio Midstream, LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	49.00%
Delaware Basin Gas Gathering System [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Appalachia Midstream Services, LLC [Member]
Description Of Business [Abstract]
Number Of Gathering Systems	11
Williams [Member]
Description Of Business [Abstract]
Parent, limited partner ownership percentage	58.00%
Parent, general partner ownership percentage	2.00%
Williams Partners L. P. [Member] \| General Partner [Member]
Description Of Business [Abstract]
Parent, general partner ownership percentage	100.00%
Access Midstream Partners Lp [Member] \| General Partner [Member]
Description Of Business [Abstract]
Parent, general partner ownership percentage	100.00%
Access Midstream [Member] \| Utica East Ohio Midstream, LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	49.00%
Access Midstream [Member] \| Delaware Basin Gas Gathering System [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Access Midstream [Member] \| Appalachia Midstream Services, LLC [Member]
Description Of Business [Abstract]
Subsidiary, ownership percentage	45.00%
Number Of Gathering Systems	$11
Northeast G And P [Member] \| Laurel Mountain Midstream, LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	69.00%
Northeast G And P [Member] \| Caiman Energy II, LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	58.00%
Atlantic Gulf [Member] \| Gulfstream Natural Gas System, L.L.C. [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Atlantic Gulf [Member] \| Discovery Producer Services LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	60.00%
Atlantic Gulf [Member] \| Constitution Pipeline Company LLC [Member]
Description Of Business [Abstract]
Variable Interest Entity Ownership Percentage	41.00%
NGL And Petchem Services [Member] \| Geismar [Member]
Description Of Business [Abstract]
Subsidiary, ownership percentage	83.30%
NGL And Petchem Services [Member] \| Conway Fractionator [Member]
Description Of Business [Abstract]
Subsidiary, ownership percentage	50.00%
NGL And Petchem Services [Member] \| Overland Pass Pipeline Company LLC [Member]
Description Of Business [Abstract]
Equity Method Investment, Ownership Percentage	50.00%
Subsequent Event [Member] \| ACMP Units Into Merged Partnership Units [Member]
Description Of Business [Abstract]
Conversion Ratio									1.06152
Subsequent Event [Member] \| Publicly Held WPZ Common Units into ACMP Common Units [Member]
Description Of Business [Abstract]
Conversion Ratio									0.86672
Subsequent Event [Member] \| Privately Held WPZ Units Into ACMP Common Units [Member]
Description Of Business [Abstract]
Conversion Ratio									0.80036
Subsequent Event [Member] \| Class D WPZ Units Into WPZ Common Units [Member]
Description Of Business [Abstract]
Conversion Ratio									1

Acquisitions_Details

Acquisitions (Details) (USD $)	6 Months Ended	12 Months Ended		2 Months Ended	4 Months Ended
In Millions, except Share data, unless otherwise specified	Jul. 02, 2014	Dec. 31, 2014	Dec. 31, 2013	Feb. 17, 2012	Apr. 27, 2012	Jul. 01, 2014
Business Acquisition, Purchase Price Allocation [Abstract]
Goodwill		$1,120	$646
Northeast G&P [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Goodwill		646	646
Access Midstream [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Goodwill		474	0
Access Midstream Partners Acquisition [Member]
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Percentage Of Finite Lived Intangible Assets Impacted By Our Intent Or Ability To Renew Or Extend Arrangement						56.00%
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension	17 years
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	30 years
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Pro Forma Revenue		7,953	7,881
Business Acquisition, Pro Forma Net Income (Loss)		1,376	1,172
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		781
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		165
Access Midstream Partners Acquisition [Member] \| Interest Expense [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Combination, Acquisition Related Costs		9
Access Midstream Partners Acquisition [Member] \| Selling, General and Administrative Expenses [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Combination, Acquisition Related Costs		16
Access Midstream Partners Acquisition [Member] \| Pro Forma [Member]
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		30 years
Access Midstream Partners Acquisition [Member] \| Access Midstream [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Accounts receivable						168
Other current assets						63
Investments						5,872
Property, plant and equipment						7,015
Goodwill						474
Intangible assets						9,009
Current liabilities						-408
Debt						-4,052
Other noncurrent liabilities						-9
Identifiable net assets acquired						10,630
Access Midstream Partners Acquisition [Member] \| ACMP's subsidiaries [Member] \| Access Midstream [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Noncontrolling interest						-958
Access Midstream Partners Acquisition [Member] \| Access Midstream Partners Lp [Member] \| Access Midstream [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Noncontrolling interest						-6,544
Laser Acquisition [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired				100.00%
Business Acquisition, Cost of Acquired Entity, Cash Paid				325
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares				7,531,381
Business Acquisition, Cost of Acquired Entity, Equity Interests Issued and Issuable				441
Laser Acquisition [Member] \| Northeast G&P [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Assets held-for-sale				18
Other current assets				3
Property, plant and equipment				158
Goodwill				290
Intangible assets				318
Current liabilities				-21
Other noncurrent liabilities				0
Identifiable net assets acquired				476
Total				766
Caiman Acquisition [Member]
Business Acquisition, Pro Forma Information [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired					100.00%
Business Acquisition, Cost of Acquired Entity, Cash Paid					1,720
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares					11,779,296
Business Acquisition, Cost of Acquired Entity, Equity Interests Issued and Issuable					603
Caiman Acquisition [Member] \| Northeast G&P [Member]
Business Acquisition, Purchase Price Allocation [Abstract]
Assets held-for-sale					0
Other current assets					16
Property, plant and equipment					656
Goodwill					356
Intangible assets					1,393
Current liabilities					-94
Other noncurrent liabilities					-3
Identifiable net assets acquired					1,968
Total					2,324
Business Acquisition, Pro Forma Information [Abstract]
Business Combination, Acquisition Related Costs		$16

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Laurel Mountain [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	69.00%
Caiman Energy II LLC [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	58.00%
Variable Interest Entity, Primary Beneficiary [Member] \| Cash and cash equivalents [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	113	$84
Variable Interest Entity, Primary Beneficiary [Member] \| Accounts receivable [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	52	0
Variable Interest Entity, Primary Beneficiary [Member] \| Other current assets [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	3	0
Variable Interest Entity, Primary Beneficiary [Member] \| Property, plant, and equipment, net [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	2,794	1,001
Variable Interest Entity, Primary Beneficiary [Member] \| Goodwill [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	103	0
Variable Interest Entity, Primary Beneficiary [Member] \| Intangible assets, net [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	1,493	0
Variable Interest Entity, Primary Beneficiary [Member] \| Other noncurrent assets [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	14	0
Variable Interest Entity, Primary Beneficiary [Member] \| Accounts payable [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-48	-122
Variable Interest Entity, Primary Beneficiary [Member] \| Accrued liabilities [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-36	-3
Variable Interest Entity, Primary Beneficiary [Member] \| Current deferred revenue [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-45	-10
Variable Interest Entity, Primary Beneficiary [Member] \| Asset retirement obligation [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-94	0
Variable Interest Entity, Primary Beneficiary [Member] \| Noncurrent deferred income taxes [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-13	0
Variable Interest Entity, Primary Beneficiary [Member] \| Noncurrent deferred revenue associated with customer advance payments [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	-395	-115
Variable Interest Entity, Primary Beneficiary [Member] \| Gulfstar One [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	51.00%
Variable Interest Entity, Primary Beneficiary [Member] \| Gulfstar One [Member] \| Estimated Remaining Construction Costs For Variable Interest Entity [Member]
Variable Interest Entity [Line Items]
Estimated remaining construction costs	150
Variable Interest Entity, Primary Beneficiary [Member] \| Constitution Pipeline Company LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	41.00%
Variable Interest Entity, Primary Beneficiary [Member] \| Constitution Pipeline Company LLC [Member] \| Estimated Remaining Construction Costs For Variable Interest Entity [Member]
Variable Interest Entity [Line Items]
Estimated remaining construction costs	628
Variable Interest Entity, Primary Beneficiary [Member] \| Cardinal Gas Services LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	66.00%
Variable Interest Entity, Primary Beneficiary [Member] \| Jackalope Gas Gathering Services LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Ownership Percentage	50.00%

Allocation_of_Net_Income_and_D2

Allocation of Net Income and Distributions (Details) (USD $)	12 Months Ended						1 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Feb. 13, 2015
Allocation of net income to general partner:
Net income	$1,284		$1,119		$1,291
NetIncomeApplicableToPreMergerOperations	-95		0		0
Pre-partnership net income allocated to general partner interest	-15		-49		-244
Net income applicable to noncontrolling interests	-96		-3		0
Costs charged directly to general partner	1		1		1
Income subject to 2% allocation of general partner interest	1,079		1,068		1,048
General partner's share of net income	2.00%		2.00%		2.00%
General partner's allocated share of net income before items directly allocable to general partner interest	22		21		21
Priority allocations, including incentive distributions, paid to general partner	641		387		355
Net Reimbursable Costs to General Partner	-1		-1		-1
NetIncomeApplicableToPreMergerOperations	95		0		0
Net Income Applicable To Pre Partnership Operations Allocated To General Partner	15		49		244
Net income allocated to general partner's equity	772		456		619
Net income	1,284		1,119		1,291
Net income allocated to general partner's equity	772		456		619
Net Income Allocated To Class D Limited Partners' Equity	62	[1]	0	[1]	0	[1]
Net income applicable to noncontrolling interests	96		3		0
Net income allocated to common limited partners' equity	354		660		672
ReconciliationAdjustmentsForNetIncomeAllocation [Abstract]
Incentive distributions paid	640		383		355
Incentive distributions declared	-626	[2]	-432	[2]	-382	[2]
Class D issuance timing	-9		0		0
Net Income (Loss) Allocated to Limited Partners	359		611		645
Distributions Made to Members or Limited Partners [Abstract]
Total Cash Distributions	2,448		1,846		1,440
Amortization of beneficial conversion feature of Class D units	0
Class D [Member]
Allocation of net income to general partner:
Net income	62		0		0
Net income	62		0		0
Distributions Made to Members or Limited Partners [Abstract]
Amortization of beneficial conversion feature of Class D units	$49
Class D Units Issued In Lieu Of Cash Distributions	1,377,893
Subsequent Event [Member]
Distributions Made to Members or Limited Partners [Abstract]
Per Unit Distribution (Paid)							$0.85

[1]	The net income allocated to Pre-merger WPZ Class D limited partners includes $49 million for the year ended DecemberB 31, 2014, related to the amortization of the beneficial conversion feature associated with the Pre-merger WPZ Class D units.
[2]	Following the completion of the Merger, we paid a cash distribution of $0.85 per unit on February 13, 2015, on our outstanding common units to unitholders of record at the close of business on February 9, 2015. For the purpose of determining the Allocation of net income to common units for the calculation of earnings per unit, the incentive distribution declared for the fourth quarter of 2014 reflects only the portion of the total incentive distribution associated with the Pre-merger WPZ common units exchanged in the Merger.

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of Related Party Transactions Abstract [Line Items]
Trade accounts and notes receivable - net	$905	$568
Revenue	13	0	0
Product costs	186	147	171
Operating and maintenance expenses	413	339	275
Accounts payable - trade	137	104
Proceeds	11	12	15
Contribution receivable	3
Employee direct costs [Member]
Summary of Related Party Transactions Abstract [Line Items]
Selling, general, and administrative expenses	331	270	308
Employee allocated costs [Member]
Summary of Related Party Transactions Abstract [Line Items]
Selling, general, and administrative expenses	171	169	190
Reorganization-related allocated costs [Member]
Summary of Related Party Transactions Abstract [Line Items]
Selling, general, and administrative expenses	2	26
Equity method investees [Member]
Summary of Related Party Transactions Abstract [Line Items]
Accounts payable - trade	13	13
Service costs	75	67	75
Common management [Member]
Summary of Related Party Transactions Abstract [Line Items]
Revenue	115	131
Product costs		13
Common management [Member] \| Silverthorne Energy Partners LP [Member]
Summary of Related Party Transactions Abstract [Line Items]
Revenue		61
Reimbursable maintenance costs for certain government projects [Member]
Summary of Related Party Transactions Abstract [Line Items]
Maximum potential obligation	$50

Investments_Details

Investments (Details) (USD $)	12 Months Ended					6 Months Ended
Investments (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014
Investments
Investments	$8,399,000,000		$2,187,000,000			$8,399,000,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	3,700,000,000					3,700,000,000
Equity Method Investment, payments to purchase or contributions	468,000,000		439,000,000		471,000,000
Equity Earnings (Losses)
Equity earnings (losses)	228,000,000		104,000,000		111,000,000
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	344,000,000		154,000,000		172,000,000
Summarized Financial Position of Equity Method Investments
Current assets	599,000,000		412,000,000			599,000,000
Noncurrent assets	9,135,000,000		5,956,000,000			9,135,000,000
Current liabilities	-850,000,000		-264,000,000			-850,000,000
Noncurrent liabilities	-954,000,000		-1,305,000,000			-954,000,000
Summarized Results of Operations of Equity Method Investments
Gross revenue	1,623,000,000		1,333,000,000		1,213,000,000
Operating income	534,000,000		367,000,000		378,000,000
Net income	460,000,000		291,000,000		309,000,000
Pre-merger ACMP [Member]
Equity Earnings (Losses)
Equity earnings (losses)						146,000,000
Adjustment For Amortization Of Difference Between Carrying Amount And Underlying Equity [Member] \| Pre-merger ACMP [Member]
Equity Earnings (Losses)
Equity earnings (losses)						-49,000,000
Appalachia Midstream Services, LLC [Member]
Investments
Investments	3,033,000,000	[1]	0	[1]		3,033,000,000	[1]
Number Of Gathering Systems	11
Equity Method Investment, payments to purchase or contributions	84,000,000		0		0
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	120,000,000		0		0
Appalachia Midstream Services, LLC [Member] \| Minimum [Member]
Investments
Investment, Ownership Percentage	33.75%					33.75%
Appalachia Midstream Services, LLC [Member] \| Minimum [Member] \| Application Of The Equity-Method Of Accounting [Member]
Investments
Investment, Ownership Percentage	50.00%					50.00%
Appalachia Midstream Services, LLC [Member] \| Maximum [Member]
Investments
Investment, Ownership Percentage	67.50%					67.50%
Appalachia Midstream Services, LLC [Member] \| Average [Member]
Investments
Investment, Ownership Percentage	45.00%					45.00%
Delaware Basin Gas Gathering System [Member]
Investments
Investments	1,478,000,000	[1]	0	[1]		1,478,000,000	[1]
Investment, Ownership Percentage	50.00%					50.00%
Equity Method Investment, payments to purchase or contributions	20,000,000		0		0
Utica East Ohio Midstream, LLC [Member]
Investments
Investments	1,411,000,000	[1]	0	[1]		1,411,000,000	[1]
Investment, Ownership Percentage	49.00%					49.00%
Equity Method Investment, payments to purchase or contributions	57,000,000		0		0
Discovery Producer Services LLC [Member]
Investments
Investments	602,000,000	[2]	527,000,000	[2]		602,000,000	[2]
Investment, Ownership Percentage	60.00%					60.00%
Equity Method Investment, payments to purchase or contributions	106,000,000		193,000,000		169,000,000
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	36,000,000		12,000,000		21,000,000
Discovery Producer Services LLC [Member] \| Proportionate Share Of Amounts Remaining For Capital Projects [Member]
Investments
Proportionate share of amounts remaining for capital projects	98,000,000					98,000,000
Laurel Mountain Midstream, LLC [Member]
Investments
Investments	459,000,000	[2]	481,000,000	[2]		459,000,000	[2]
Investment, Ownership Percentage	69.00%					69.00%
Equity Method Investment, payments to purchase or contributions	12,000,000		42,000,000		174,000,000
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	39,000,000		0		0
Laurel Mountain Midstream, LLC [Member] \| Proportionate Share Of Amounts Remaining For Capital Projects [Member]
Investments
Proportionate share of amounts remaining for capital projects	92,000,000					92,000,000
Overland Pass Pipeline Company LLC [Member]
Investments
Investments	453,000,000		452,000,000			453,000,000
Investment, Ownership Percentage	50.00%					50.00%
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	27,000,000		27,000,000		28,000,000
Caiman Energy II LLC [Member]
Investments
Investments	432,000,000	[2]	256,000,000	[2]		432,000,000	[2]
Investment, Ownership Percentage	58.00%					58.00%
Equity Method Investment, payments to purchase or contributions	175,000,000		192,000,000		69,000,000
Gulfstream Natural Gas System, L.L.C. [Member]
Investments
Investments	317,000,000		333,000,000			317,000,000
Investment, Ownership Percentage	50.00%					50.00%
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	81,000,000		81,000,000		78,000,000
Other [Member]
Investments
Investments	214,000,000		138,000,000			214,000,000
Aux Sable Liquid Products LP [Member]
Dividends and distributions
Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital	$15,000,000		$20,000,000		$28,000,000

[1]	These are Pre-merger ACMP investments. The Appalachia Midstream Investments include investments in 11 different gathering systems in the Marcellus Shale. Ownership interests range from 33.75 percent to 67.50 percent, resulting in an overall approximate average interest of 45 percent. For those investments where we own in excess of 50 percent, we apply the equity-method of accounting due to the significant participation rights of our partners such that we do not control. (See Note 1 b General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies.)
[2]	We account for these investments under the equity method due to the significant participatory rights of our partners such that we do not control or are otherwise not the primary beneficiary of the investments.

Other_Income_and_Expenses_Deta

Other Income and Expenses (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Loss related to sale of certain assets	$57	$6	$7
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	34	20	15
Access Midstream [Member]
Segment Reporting Information [Line Items]
Loss related to sale of certain assets	10	0	0
Impairment of certain assets held for sale	12	0	0
Access Midstream [Member] \| Employee costs [Member] \| Selling, General and Administrative Expenses [Member]
Segment Reporting Information [Line Items]
Business Combination, Integration Related Costs	15
Access Midstream [Member] \| Employee costs [Member] \| Operation and maintenance [Member]
Segment Reporting Information [Line Items]
Business Combination, Integration Related Costs	15
Access Midstream [Member] \| Merger [Member]
Segment Reporting Information [Line Items]
Business Combination, Integration Related Costs	11
Northeast G&P [Member]
Segment Reporting Information [Line Items]
Contingency gain settlement	-154	0	0
Impairment of certain assets	30	0	0
Net Gain Related To Acreage Dedication Release	-12	0	0
Northeast G&P [Member] \| Producer claim [Member]
Segment Reporting Information [Line Items]
Loss associated with a producer claim	0	25	0
Atlantic-Gulf [Member]
Segment Reporting Information [Line Items]
Impairment of certain assets	10	0	0
Amortization of regulatory asset associated with asset retirement obligations	33	30	7
Project feasibility costs	2	4	21
Capitalization of project feasibility costs previously expensed	-5	-1	-19
Atlantic-Gulf [Member] \| Asset Impairment for Regulatory Action [Member]
Segment Reporting Information [Line Items]
Impairment of certain assets	-3	12	0
Insurance recoveries	0	-16	0
NGL & Petchem Services [Member] \| Geismar Incident [Member]
Segment Reporting Information [Line Items]
Insurance recoveries	-246	-50
Insurance deductible expense		13
Insurable Expenses in Excess of our Deductibles	14	10
NGL & Petchem Services [Member] \| Geismar Incident [Member] \| Property Damage And Business Interruption Coverage [Member]
Segment Reporting Information [Line Items]
Maximum insurance recoverable amount	500
NGL & Petchem Services [Member] \| Geismar Incident [Member] \| Property Damage [Member]
Segment Reporting Information [Line Items]
Insurance deductibles	10
NGL & Petchem Services [Member] \| Geismar Incident [Member] \| Business Interruption [Member]
Segment Reporting Information [Line Items]
Duration of waiting period before business interruption coverage begins	60 days
NGL & Petchem Services [Member] \| Geismar Incident [Member] \| General Liability Coverage [Member]
Segment Reporting Information [Line Items]
Maximum insurance recoverable amount	610
Insurance deductibles	2
NGL & Petchem Services [Member] \| Geismar Incident [Member] \| Workers Compensation Coverage [Member]
Segment Reporting Information [Line Items]
Insurance deductibles	$1

Provision_Benefit_Table_Detail

Provision (Benefit) Table (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
State	$3	$2	$11
Foreign	1	-22	26
Total	4	-20	37
Deferred:
State	8	15	0
Foreign	17	35	5
Total	25	50	5
Provision (benefit) for income taxes	$29	$30	$42

Reconciliations_To_Recorded_Pr

Reconciliations To Recorded Provision for Income Taxes (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Provision at statutory rate	$462	$402	$467
Increases (decreases) in taxes resulting from:
Income not subject to U.S. federal tax	-462	-402	-467
State income taxes	11	17	11
Foreign operations - net	18	13	31
Provision (benefit) for income taxes	$29	$30	$42

Provision_Benefit_for_Income_T2

Provision (Benefit) for Income Taxes Texuals (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Provision (Benefit) for Income Taxes (Textuals) [Abstract]
Deferred tax provision related to tax law change	$14
Income (Loss) from Continuing Operations before Income Taxes, Foreign		72	61	96
Deferred Tax Liabilities, Property, Plant and Equipment		133	117	72
Income Taxes Paid, Net		($28)	$2	$54

Benefit_Plans_Details

Benefit Plans (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost Recognized	$25	$16	$19
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	1,500	1,400
Defined Benefit Plan, Funded Status of Plan	-251	-143
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	28	44	41
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	233	213
Defined Benefit Plan, Funded Status of Plan	-25	-12
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$14	$4	($4)

Inventories_Details

Inventories (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Inventory Net [Abstract]
Natural gas liquids, olefins, and natural gas in underground storage	$150	$111
Materials, supplies, and other	81	83
Total Inventories	$231	$194

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Details PPE) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment
Property, plant, and equipment, at cost	$35,479		$25,062
Accumulated depreciation	-8,157		-7,437
Property, plant, and equipment - net	27,322		17,625
Depreciation and amortization	944		729	690
Nonregulated [Member] \| Natural gas gathering and processing facilities [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	18,717		9,172
Nonregulated [Member] \| Natural gas gathering and processing facilities [Member] \| Minimum [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	5 years	[1]
Nonregulated [Member] \| Natural gas gathering and processing facilities [Member] \| Maximum [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	40 years	[1]
Nonregulated [Member] \| Construction in Progress [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	2,115		2,727
Nonregulated [Member] \| Other Capitalized Property Plant and Equipment [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	1,459		964
Nonregulated [Member] \| Other Capitalized Property Plant and Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	3 years	[1]
Nonregulated [Member] \| Other Capitalized Property Plant and Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	45 years	[1]
Regulated [Member] \| Natural gas transmission facilities [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	10,867		10,633
Regulated [Member] \| Natural gas transmission facilities [Member] \| Minimum [Member]
Property, Plant and Equipment
Regulated Property Plant And Equipment Depreciation Rate1	1.20%	[1]
Regulated [Member] \| Natural gas transmission facilities [Member] \| Maximum [Member]
Property, Plant and Equipment
Regulated Property Plant And Equipment Depreciation Rate1	6.97%	[1]
Regulated [Member] \| Construction in Progress [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	985		273
Regulated [Member] \| Other Capitalized Property Plant and Equipment [Member]
Property, Plant and Equipment
Property, plant, and equipment, at cost	1,336		1,293
Regulated [Member] \| Other Capitalized Property Plant and Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment
Regulated Property Plant And Equipment Depreciation Rate1	1.35%	[1]
Regulated [Member] \| Other Capitalized Property Plant and Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment
Regulated Property Plant And Equipment Depreciation Rate1	33.33%	[1]
Regulated [Member] \| Excess Of Original Cost Of Regulated Facilities [Member]
Property, Plant and Equipment
Property, plant, and equipment - net	$746		$785
Period of straight-line amortization	40 years

[1]	Estimated useful life and depreciation rates are presented as of DecemberB 31, 2014. Depreciation rates for regulated assets are prescribed by the FERC.

Property_Plant_and_Equipment_D1

Property, Plant, and Equipment (Details ARO) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$561		$579
Liabilities incurred	101		8
Liabilities settled	-21	[1]	-31	[1]
Accretion expense	44		53
Revisions	146	[2]	-48	[2]
Ending balance	831		561
Charges Related To Leak At Underground Natural Gas Storage Facility [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liabilities settled	-7		-25
Revisions			9
Asset Retirement Obligation Costs [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Transco's annual funding commitment for ARO	$36

[1]	For 2014 and 2013, liabilities settled include $7 million and $25 million, respectively, related to the abandonment of certain of Transcobs natural gas storage caverns that are associated with a leak in 2010.
[2]	The 2013 revision also includes an increase of $9 million related to changes in the timing and method of abandonment on certain of Transcobs natural gas storage caverns that were associated with a leak in 2010.

Goodwill_and_Other_Intangible_2

Goodwill and Other Intangible Assets Goodwill (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill	$1,120	$646
Goodwill, Acquired During Period	474
Access Midstream [Member]
Goodwill [Line Items]
Goodwill	474	0
Goodwill, Acquired During Period	474
Northeast G And P [Member]
Goodwill [Line Items]
Goodwill	646	646
Goodwill, Acquired During Period	$0

Goodwill_and_Other_Intangible_3

Goodwill and Other Intangible Assets Other Intangible Assets (Details) (USD $)	12 Months Ended			6 Months Ended	2 Months Ended	4 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 02, 2014	Feb. 17, 2012	Apr. 27, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$207	$60	$43
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	357
Finite-Lived Intangible Assets, Amortization Expense, Year Two	357
Finite-Lived Intangible Assets, Amortization Expense, Year Three	357
Finite-Lived Intangible Assets, Amortization Expense, Year Four	357
Finite-Lived Intangible Assets, Amortization Expense, Year Five	357
Contractual customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	10,761	1,747
Finite-Lived Intangible Assets, Accumulated Amortization	($310)	($105)
Access Midstream Partners Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				30 years
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension				17 years
Laser Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life					30 years
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension					9 years
Caiman Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life						30 years
Acquired Finite-lived Intangible Asset, Weighted-Average Period before Renewal or Extension						18 years

LongTerm_Debt_Details_1

Long-Term Debt (Details 1) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Nov. 15, 2013	Mar. 04, 2014	Jun. 27, 2014
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Nov. 15, 2013	Mar. 04, 2014	Jun. 27, 2014
Debt Instrument [Line Items]
Capital Lease Obligations	$5		$0
Net unamortized debt premium (discount)	207	[1]	-21	[1]
Long-term debt, including current portion	16,330		9,057
Long-term Debt and Capital Lease Obligations, Current	-4		0
Long-term debt	16,326		9,057
Transcontinental Gas Pipe Line Company, LLC [Member] \| 6.4% Senior Unsecured Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt	200		200
Long-term debt interest rate	6.40%
Transcontinental Gas Pipe Line Company, LLC [Member] \| 6.05% Senior Unsecured Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	250		250
Long-term debt interest rate	6.05%
Transcontinental Gas Pipe Line Company, LLC [Member] \| 7.08% Debentures due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt	8		8
Long-term debt interest rate	7.08%
Transcontinental Gas Pipe Line Company, LLC [Member] \| 7.25% Debentures due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt	200		200
Long-term debt interest rate	7.25%
Transcontinental Gas Pipe Line Company, LLC [Member] \| 5.4% Senior Unsecured Notes due 2041 [Member]
Debt Instrument [Line Items]
Long-term debt	375		375
Long-term debt interest rate	5.40%
Transcontinental Gas Pipe Line Company, LLC [Member] \| 4.45% Senior Unsecured Notes due 2042 [Member]
Debt Instrument [Line Items]
Long-term debt	400		400
Long-term debt interest rate	4.45%
Northwest Pipeline LLC [Member] \| 7% Senior Unsecured Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt	175		175
Long-term debt interest rate	7.00%
Northwest Pipeline LLC [Member] \| 5.95% Senior Unsecured Notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	185		185
Long-term debt interest rate	5.95%
Northwest Pipeline LLC [Member] \| 6.05% Senior Unsecured Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	250		250
Long-term debt interest rate	6.05%
Northwest Pipeline LLC [Member] \| 7.125% Debentures due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	85		85
Long-term debt interest rate	7.13%
Williams Partners L.P. [Member]
Debt Instrument [Line Items]
Credit facility loans	640	[2]	0	[2]
Williams Partners L.P. [Member] \| 3.8% Senior Unsecured Notes due 2015 [Member]
Debt Instrument [Line Items]
Long-term debt	750	[3]	750
Long-term debt interest rate	3.80%
Williams Partners L.P. [Member] \| 7.25% Senior Unsecured Notes due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	600		600
Long-term debt interest rate	7.25%
Williams Partners L.P. [Member] \| 5.25% Senior Unsecured Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	1,500		1,500
Long-term debt interest rate	5.25%
Williams Partners L.P. [Member] \| 4.125% Senior Unsecured Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	600		600
Long-term debt interest rate	4.13%
Williams Partners L.P. [Member] \| 5.875% Senior Unsecured Notes due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	750	[2]	0	[2]
Long-term debt interest rate	5.88%
Williams Partners L.P. [Member] \| 4% Senior Unsecured Notes due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	500		500
Long-term debt interest rate	4.00%
Williams Partners L.P. [Member] \| 3.35% Senior Unsecured Notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	750		750
Long-term debt interest rate	3.35%
Williams Partners L.P. [Member] \| 6.125% Senior Unsecured Notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	750	[2]	0	[2]
Long-term debt interest rate	6.13%
Williams Partners L.P. [Member] \| 4.875% Senior Unsecured Notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	1,400	[2]	0	[2]
Long-term debt interest rate	4.88%
Williams Partners L.P. [Member] \| 4.5% Senior Unsecured Notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	600		600
Long-term debt interest rate	4.50%				4.50%
Williams Partners L.P. [Member] \| 4.3% Senior Unsecured Notes Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	1,000		0
Long-term debt interest rate	4.30%					4.30%
Williams Partners L.P. [Member] \| 4.875% Senior Unsecured Notes due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	750	[2]	0	[2]
Long-term debt interest rate	4.88%
Williams Partners L.P. [Member] \| 3.9% Senior Unsecured Notes due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt	750		0
Long-term debt interest rate	3.90%						3.90%
Williams Partners L.P. [Member] \| 6.3% Senior Unsecured Notes due 2040 [Member]
Debt Instrument [Line Items]
Long-term debt	1,250		1,250
Long-term debt interest rate	6.30%
Williams Partners L.P. [Member] \| 5.8% Senior Unsecured Notes due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt	400		400
Long-term debt interest rate	5.80%				5.80%
Williams Partners L.P. [Member] \| 5.4% Senior Unsecured Notes Due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt	500		0
Long-term debt interest rate	5.40%					5.40%
Williams Partners L.P. [Member] \| 4.9% Senior Unsecured Notes due 2045 [Member]
Debt Instrument [Line Items]
Long-term debt	$500		$0
Long-term debt interest rate	4.90%						4.90%

[1]	Includes premium related to the fair value of Pre-merger ACMP debt. See Note 2 b Acquisitions.
[2]	These notes and credit facility loans are associated with Pre-merger ACMP. See Note 1 b General, Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies and Note 2 b Acquisitions.
[3]	Presented as long-term debt due to our intent and ability to refinance.

LongTerm_Debt_Maturities_Detai

Long-Term Debt Maturities (Details 2) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified	Dec. 31, 2014
Long-term Debt, by Maturity [Abstract]
2015	$0
2016	375
2017	785
2018	1,140
2019	$0

LongTerm_Debt_Issuances_and_Re

Long-Term Debt Issuances and Retirements (Details 3) (Williams Partners L. P. [Member], USD $)	0 Months Ended
In Millions, unless otherwise specified	Feb. 15, 2015	Dec. 31, 2014	Jun. 27, 2014	Mar. 04, 2014	Nov. 15, 2013
3.8% Senior Unsecured Notes due 2015 [Member]
Debt Instrument [Line Items]
Long-term debt interest rate		3.80%
3.8% Senior Unsecured Notes due 2015 [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Long-term debt retired	$750
Long-term debt interest rate	3.80%
3.9% Senior Unsecured Notes due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt face amount			750
Long-term debt interest rate		3.90%	3.90%
4.9% Senior Unsecured Notes due 2045 [Member]
Debt Instrument [Line Items]
Long-term debt face amount			500
Long-term debt interest rate		4.90%	4.90%
4.3% Senior Unsecured Notes Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt face amount				1,000
Long-term debt interest rate		4.30%		4.30%
5.4% Senior Unsecured Notes Due 2044 [Member]
Debt Instrument [Line Items]
Long-term debt face amount				500
Long-term debt interest rate		5.40%		5.40%
4.5% Senior Unsecured Notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt face amount					600
Long-term debt interest rate		4.50%			4.50%
5.8% Senior Unsecured Notes due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt face amount					$400
Long-term debt interest rate		5.80%			5.80%

Credit_Facility_and_Commercial

Credit Facility and Commercial Paper (Details 4) (USD $)	0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Feb. 02, 2015	Dec. 31, 2014	Dec. 31, 2013	4-May-15	Feb. 24, 2015	Feb. 03, 2015
Credit Facility and Commercial Paper [Line Items]
Commercial paper, outstanding		$798	$225
Northwest Pipeline LLC [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		500
Northwest Pipeline LLC [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	500
Maximum ratio of debt to capitalization	65.00%
Transcontinental Gas PipeLine Company, LLC [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		500
Transcontinental Gas PipeLine Company, LLC [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	500
Maximum ratio of debt to capitalization	65.00%
Williams Partners L.P. [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		2,500
Credit facility, loans outstanding		0
Additional amount by which credit facility can be increased		500
Williams Partners L.P. [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	3,500
Credit facility, loans outstanding				0	1,300
Additional amount by which credit facility can be increased	500
Maximum ratio of debt to EBITDA	5
Maximum ratio of debt to EBITDA after acquisition	5.5
Williams Partners L.P. [Member] \| Rate addition to federal funds effective rate [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate	0.50%
Williams Partners L.P. [Member] \| Rate addition to London interbank offered rate (LIBOR) [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate	1.00%
Williams Partners L.P. [Member] \| Commercial Paper [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		2,000
Commercial paper, outstanding		798	225
Commercial paper, weighted average interest rate		0.92%	0.42%
Commercial paper, maximum maturity		397 days
Williams Partners L.P. [Member] \| Commercial Paper [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	3,000
Commercial paper, outstanding				536	1,800
Williams Partners L.P. [Member] \| Letter of Credit [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		1,300
Credit facility, letters of credit outstanding		0
Williams Partners L.P. [Member] \| Letter of Credit [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	1,125
Williams Partners L.P. [Member] \| Letters Of Credit Under Certain Bilateral Bank Agreements [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, letters of credit outstanding		1
Williams Partners L.P. [Member] \| Swing Line Advances [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity	150
Williams Partners L.P. [Member] \| Short-term facility [Member] \| Subsequent Event [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity						1,500
Access Midstream Partners Lp [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		1,750
Credit facility, loans outstanding		640
Additional amount by which credit facility can be increased		250
Access Midstream Partners Lp [Member] \| Rate addition to federal funds effective rate [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		0.50%
Access Midstream Partners Lp [Member] \| Rate addition to London interbank offered rate (LIBOR) [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		1.00%
Access Midstream Partners Lp [Member] \| Rate plus a margin [Member] \| Minimum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		0.50%
Access Midstream Partners Lp [Member] \| Rate plus a margin [Member] \| Maximum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		1.50%
Access Midstream Partners Lp [Member] \| Eurodollar rate plus a margin [Member] \| Minimum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		1.50%
Access Midstream Partners Lp [Member] \| Eurodollar rate plus a margin [Member] \| Maximum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, basis spread on variable rate		2.50%
Access Midstream Partners Lp [Member] \| Leverage-based pricing grid [Member] \| Minimum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, unused capacity commitment fee percentage		0.25%
Access Midstream Partners Lp [Member] \| Leverage-based pricing grid [Member] \| Maximum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, unused capacity commitment fee percentage		0.38%
Access Midstream Partners Lp [Member] \| Ratings-based pricing grid [Member] \| Minimum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, unused capacity commitment fee percentage		0.15%
Access Midstream Partners Lp [Member] \| Ratings-based pricing grid [Member] \| Maximum [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, unused capacity commitment fee percentage		0.30%
Access Midstream Partners Lp [Member] \| Letter of Credit [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		200
Credit facility, letters of credit outstanding		2
Access Midstream Partners Lp [Member] \| Swing Line Advances [Member]
Credit Facility and Commercial Paper [Line Items]
Credit facility, capacity		100
Credit facility, loans outstanding		$0

Cash_Payments_For_Interest_Net

Cash Payments For Interest (Net of Amounts Capitalized) (Details 5) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Cash payments for interest (net of amounts capitalized)	$499	$366	$381

LeasesLessee_Details_6

Leases-Lessee (Details 6) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015	$72
2016	62
2017	49
2018	37
2019	33
Thereafter	129
Total	382
Operating leases [Abstract]
Total rent expense	$101	$51	$46

Partners_Capital_Details_Textu

Partners' Capital (Details Textuals) (USD $)	1 Months Ended			12 Months Ended
Partners' Capital (Details Textuals) (USD $)	Aug. 31, 2014	Aug. 31, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Partners' Capital Account, Units, Sold in Public Offering		21,500,000
Partners' Capital Account, Units, Sold in Private Placement			3,000,000
Percentage of outstanding units voting as a single class to remove general partner				66.67%
Days after the end of each quarter to receive cash distributions				45 days
Net Proceeds from Issuance of Common Limited Partners Units	$55,000,000	$1,200,000,000	$760,000,000	$55,000,000	$1,962,000,000	$2,559,000,000
Offering Costs, Partnership Interests	$554,000
Partners' Capital Account, Units, Sale of Units	1,080,448		14,250,000
Option on Securities [Member]
Business Acquisition [Line Items]
Partners' Capital Account, Units, Sold in Public Offering		3,225,000	1,687,500

Partners_Capital_Incentive_Dis

Partners' Capital Incentive Distributions Quarterly Target Amount (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
First Target Distribution [Member] \| Minimum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Unitholders	98.00%
General Partner	2.00%
Quarterly Distribution Target Amount	$0.34
First Target Distribution [Member] \| Maximum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Unitholders	98.00%
General Partner	2.00%
Quarterly Distribution Target Amount	$0.39
Second Target Distribution [Member] \| Minimum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Unitholders	85.00%
General Partner	15.00%
Quarterly Distribution Target Amount	$0.39
Second Target Distribution [Member] \| Maximum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Quarterly Distribution Target Amount	$0.42
Third Target Distribution [Member] \| Minimum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Unitholders	75.00%
General Partner	25.00%
Quarterly Distribution Target Amount	$0.42
Third Target Distribution [Member] \| Maximum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Quarterly Distribution Target Amount	$0.51
Thereafter [Member] \| Minimum [Member]
Incentive Distribution Target Amount Per Unit [Line Items]
Unitholders	50.00%
General Partner	50.00%
Quarterly Distribution Target Amount	$0.51

EquityBased_Compensation_Detai

Equity-Based Compensation (Details) (USD $)	12 Months Ended			6 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Williams Companies Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$14	$12	$13
Access Midstream Partners Long Term Incentive Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				11
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	65			65
Estimated forfeitures under employee stock-based awards	$6			$6
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition				2 years 4 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted, Units				1.3
Forfeited, Units				0
Vested, Units				0
Nonvested at end of period,Units	1.3			1.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted, Weighted Average Grant Date Fair Value				$59.67
Forfeited, Weighted Average Grant Date Fair Value				$63.89
Vested, Weighted Average Grant Date Fair Value				$63.75
Nonvested at end of period, Weighted Average Grant Date Fair Value	$59.35			$59.35
Access Midstream Partners Long Term Incentive Plan [Member] \| Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				1 year
Access Midstream Partners Long Term Incentive Plan [Member] \| Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				4 years

Fair_Value_Measurements_Guaran2

Fair Value Measurements Guarantees and Concentration of Credit Risk (Details) (USD $)	12 Months Ended				3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Additional disclosures:
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$0		$0		$0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0		0		0
Accounts and Notes Receivable
Receivables by product or service	905		568		905
Customer Concentration Risk [Member] \| Accounts receivable [Member]
Accounts and Notes Receivable
Number Of Major Customers - Receivables	1
Receivables by product or service	308				308
Revenues
Number Of Major Customers - Revenues	1
NGLs, natural gas, and related products and services [Member]
Accounts and Notes Receivable
Receivables by product or service	728		341		728
Transportation of natural gas and related products [Member]
Accounts and Notes Receivable
Receivables by product or service	175		193		175
Other Receivable [Member]
Accounts and Notes Receivable
Receivables by product or service	2		34		2
Carrying Amount [Member]
Additional disclosures:
Notes receivable and other	5		7		5
Long-term debt	-16,325	[1]	-9,057		-16,325	[1]
Fair Value [Member]
Additional disclosures:
Notes receivable and other	4		7		4
Long-term debt	-16,607	[1]	-9,581		-16,607	[1]
Level 1 [Member]
Additional disclosures:
Notes receivable and other	0		1		0
Long-term debt	0	[1]	0		0	[1]
Level 2 [Member]
Additional disclosures:
Notes receivable and other	4		6		4
Long-term debt	-16,607	[1]	-9,581		-16,607	[1]
Level 3 [Member]
Additional disclosures:
Notes receivable and other	0		0		0
Long-term debt	0	[1]	0		0	[1]
Fair Value, Measurements, Recurring [Member] \| Carrying Amount [Member]
Measured on a recurring basis:
ARO Trust investments	48		33		48
Fair Value, Measurements, Recurring [Member] \| Carrying Amount [Member] \| Not Designated as Hedging Instrument [Member]
Measured on a recurring basis:
Energy derivative assets	3		3		3
Energy derivative liabilities	-2		-3		-2
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member]
Measured on a recurring basis:
ARO Trust investments	48		33		48
Fair Value, Measurements, Recurring [Member] \| Fair Value [Member] \| Not Designated as Hedging Instrument [Member]
Measured on a recurring basis:
Energy derivative assets	3		3		3
Energy derivative liabilities	-2		-3		-2
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Measured on a recurring basis:
ARO Trust investments	48		33		48
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Not Designated as Hedging Instrument [Member]
Measured on a recurring basis:
Energy derivative assets	1		0		1
Energy derivative liabilities	0		0		0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Measured on a recurring basis:
ARO Trust investments	0		0		0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Not Designated as Hedging Instrument [Member]
Measured on a recurring basis:
Energy derivative assets	0		0		0
Energy derivative liabilities	0		-1		0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Measured on a recurring basis:
ARO Trust investments	0		0		0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Not Designated as Hedging Instrument [Member]
Measured on a recurring basis:
Energy derivative assets	2		3		2
Energy derivative liabilities	-2		-2		-2
Northeast G And P [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Held-for-sale, Long Lived, Fair Value Disclosure	32				32
Additional disclosures:
Impairment of Long-Lived Assets to be Disposed of	27
Access Midstream [Member]
Additional disclosures:
Impairment of Long-Lived Assets to be Disposed of	12		0	0
Access Midstream [Member] \| Customer Concentration Risk [Member] \| Sales Revenue, Net [Member]
Accounts and Notes Receivable
Number Of Major Customers - Receivables	1
Revenues
Number Of Major Customers - Revenues	1
Consolidated revenue, major customer, percentage	9.00%
Access Midstream [Member] \| Fair Value, Measurements, Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Held-for-sale, Long Lived, Fair Value Disclosure	1				1
Additional disclosures:
Impairment of Long-Lived Assets to be Disposed of					$12
NGL And Petchem Services [Member] \| Customer Concentration Risk [Member] \| Sales Revenue, Net [Member]
Accounts and Notes Receivable
Number Of Major Customers - Receivables				1
Revenues
Number Of Major Customers - Revenues				1
Consolidated revenue, major customer, percentage	5.00%		9.00%	14.00%

[1]	(1) Excludes capital leases

Contingent_Liabilities_Details

Contingent Liabilities (Details) (USD $)	0 Months Ended
Contingent Liabilities (Details) (USD $)	Sep. 12, 2014	Dec. 31, 2014	Dec. 01, 2014	Dec. 11, 2013
Contingent Liabilities [Line Items]
Accrued environmental loss liabilities		$19,000,000
Commitments For Construction And Acquisition Of Property Plant And Equipment		552,000,000
Environmental Protection Agency [Member]
Contingent Liabilities [Line Items]
Accrued environmental loss liabilities		11,000,000
Natural gas underground storage facilities [Member]
Contingent Liabilities [Line Items]
Accrued environmental loss liabilities		8,000,000
Geismar [Member]
Contingent Liabilities [Line Items]
Penalty Assessment			194,306
Geismar Incident [Member]
Contingent Liabilities [Line Items]
Notice of Penalty				99,000
Litigation Settlement, Amount	$36,000

Segment_Disclosures_Geographic

Segment Disclosures Geographic Information (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	$7,409	$6,835	$7,471
Long-lived assets	38,893	19,913	17,507
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	7,212	6,685	7,320
Long-lived assets	37,798	18,776	16,637
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	197	150	151
Long-lived assets	$1,095	$1,137	$870

Segment_Disclosures_Recon_from

Segment Disclosures Recon from Segment to Consolidated (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of segment revenues and segment profit (loss)
Revenues	$7,409	$6,835	$7,471
Segment profit (loss)	2,008	1,677	1,907
Equity earnings (losses)	228	104	111
Cost-method Investments, Realized Gain (Loss)		-3	-4
Operating income	1,609	1,407	1,610
Other financial information:
Depreciation and amortization	1,151	791	734
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	49,322	23,571
Investments	8,399	2,187
Additions to long-lived assets	20,413	3,409	5,858
Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	3,888	2,914	2,714
Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,781	1,704	1,598
Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,796	932	844
Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	3,521	3,921	4,757
Access Midstream [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	781	0	0
Access Midstream [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Access Midstream [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	781	0	0
Access Midstream [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Northeast G&P [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	450	335	168
Northeast G&P [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Northeast G&P [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	394	302	159
Northeast G&P [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	225	166	2
Atlantic-Gulf [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,497	1,414	1,371
Atlantic-Gulf [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,313	1,244	1,171
Atlantic-Gulf [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	79	70	80
Atlantic-Gulf [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	499	830	709
West [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,034	1,053	1,067
West [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	470	469	438
West [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	544	562	607
West [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	70	64	40
NGL & Petchem Services [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	126	112	108
NGL & Petchem Services [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
NGL & Petchem Services [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
NGL & Petchem Services [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	2,727	2,861	4,006
Operating Segments [Member]
Reconciliation of segment revenues and segment profit (loss)
Operating income	1,780	1,576	1,800
Operating Segments [Member] \| Access Midstream [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	781	0	0
Segment profit (loss)	265	0	0
Equity earnings (losses)	96	0	0
Cost-method Investments, Realized Gain (Loss)		0	0
Operating income	169	0	0
Other financial information:
Depreciation and amortization	296	0	0
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	23,024	0
Investments	6,004	0
Additions to long-lived assets	16,964	0	0
Operating Segments [Member] \| Access Midstream [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	781	0	0
Operating Segments [Member] \| Access Midstream [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Operating Segments [Member] \| Northeast G&P [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	681	501	170
Segment profit (loss)	212	-24	-37
Equity earnings (losses)	19	-7	-23
Cost-method Investments, Realized Gain (Loss)		0	0
Operating income	193	-17	-14
Other financial information:
Depreciation and amortization	170	132	76
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	7,314	6,229
Investments	891	737
Additions to long-lived assets	1,079	1,376	3,909
Operating Segments [Member] \| Northeast G&P [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	451	335	168
Operating Segments [Member] \| Northeast G&P [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	230	166	2
Operating Segments [Member] \| Atlantic-Gulf [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	2,354	2,349	2,455
Segment profit (loss)	635	614	574
Equity earnings (losses)	76	72	92
Cost-method Investments, Realized Gain (Loss)		0	0
Operating income	559	542	482
Other financial information:
Depreciation and amortization	379	363	381
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	11,124	10,007
Investments	985	930
Additions to long-lived assets	1,593	1,072	1,002
Operating Segments [Member] \| Atlantic-Gulf [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,501	1,424	1,383
Operating Segments [Member] \| Atlantic-Gulf [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	853	925	1,072
Operating Segments [Member] \| West [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,580	1,826	2,201
Segment profit (loss)	631	741	980
Equity earnings (losses)	0	0	0
Cost-method Investments, Realized Gain (Loss)		0	0
Operating income	631	741	980
Other financial information:
Depreciation and amortization	239	236	234
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	4,620	4,767
Investments	0	0
Additions to long-lived assets	168	210	360
Operating Segments [Member] \| West [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	1,034	1,054	1,072
Operating Segments [Member] \| West [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	546	772	1,129
Operating Segments [Member] \| NGL & Petchem Services [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	3,112	3,267	4,372
Segment profit (loss)	265	346	390
Equity earnings (losses)	37	39	42
Cost-method Investments, Realized Gain (Loss)		-3	-4
Operating income	228	310	352
Other financial information:
Depreciation and amortization	67	60	43
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	3,510	3,035
Investments	519	520
Additions to long-lived assets	601	746	571
Operating Segments [Member] \| NGL & Petchem Services [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	126	112	108
Operating Segments [Member] \| NGL & Petchem Services [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	2,986	3,155	4,264
Eliminations [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-1,099	-1,108	-1,727
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	-833	-614
Investments	0	0
Additions to long-lived assets	0	0	0
Eliminations [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-5	-11	-17
Eliminations [Member] \| Regulated Natural Gas Transportation And Storage [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-2	-9	-11
Eliminations [Member] \| Gathering and Processing [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-2	-2	-2
Eliminations [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-1,094	-1,097	-1,710
Eliminations [Member] \| Access Midstream [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Eliminations [Member] \| Access Midstream [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Eliminations [Member] \| Northeast G&P [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-1	0	0
Eliminations [Member] \| Northeast G&P [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-5	0	0
Eliminations [Member] \| Atlantic-Gulf [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-4	-10	-12
Eliminations [Member] \| Atlantic-Gulf [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-354	-95	-363
Eliminations [Member] \| West [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	-1	-5
Eliminations [Member] \| West [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-476	-708	-1,089
Eliminations [Member] \| NGL & Petchem Services [Member] \| Service [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	0	0	0
Eliminations [Member] \| NGL & Petchem Services [Member] \| Product [Member]
Reconciliation of segment revenues and segment profit (loss)
Revenues	-259	-294	-258
Corporate Non-Segment [Member]
Reconciliation of segment revenues and segment profit (loss)
Operating income	-171	-169	-190
Total assets, investments and additions to long-lived assets by reporting segment
Total assets	563	147
Investments	0	0
Additions to long-lived assets	$8	$5	$16

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	12 Months Ended			0 Months Ended		1 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 20, 2015	Apr. 15, 2015	Apr. 30, 2015	Mar. 03, 2015	4-May-15	Feb. 24, 2015	Apr. 06, 2015
Subsequent Event [Line Items]
Payments to Acquire Equity Method Investments	$468	$439	$471
Commercial paper	798	225
Cash distributions per common unit	$3.60	$3.48	$3.21
Subsequent Event [Member]
Subsequent Event [Line Items]
Cash distributions per common unit				$0.85
Subsequent Event [Member] \| 3.6% Senior Unsecured Notes due 2022 [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount							1,250
Debt Instrument, Interest Rate, Stated Percentage							3.60%
Subsequent Event [Member] \| 4% Senior Unsecured Notes due 2025 [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount							750
Debt Instrument, Interest Rate, Stated Percentage							4.00%
Subsequent Event [Member] \| 5.1% Senior Unsecured Notes due 2045 [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount							1,000
Debt Instrument, Interest Rate, Stated Percentage							5.10%
Subsequent Event [Member] \| 5.875% Senior Unsecured Notes due 2021 [Member]
Subsequent Event [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					5.88%
Repayments of Debt					783
Long-term debt retired					750
Williams Partners L.P. [Member]
Subsequent Event [Line Items]
Credit facility, loans outstanding	0
Williams Partners L.P. [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Credit facility, loans outstanding								0	1,300
Williams Partners L.P. [Member] \| Commercial Paper [Member]
Subsequent Event [Line Items]
Commercial paper	798	225
Williams Partners L.P. [Member] \| Commercial Paper [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Commercial paper								536	1,800
Utica East Ohio Midstream, LLC [Member]
Subsequent Event [Line Items]
Payments to Acquire Equity Method Investments	57	0	0
Equity Method Investment, Ownership Percentage	49.00%
Utica East Ohio Midstream, LLC [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Payments to Acquire Equity Method Investments						$575
Percentage To Be Acquired By Us Without Participation By Another [Member] \| Utica East Ohio Midstream, LLC [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Equity Method Investment, Ownership Percentage										21.00%
Percentage To Be Acquired By Us With Participation By Another [Member] \| Utica East Ohio Midstream, LLC [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Equity Method Investment, Ownership Percentage										13.00%
Percentage To Be Acquired By Another If Participation Right Is Exercised [Member] \| Utica East Ohio Midstream, LLC [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired										8.00%