Allocation of Net Income and Distributions (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Apr. 20, 2015
Amortization of beneficial conversion feature of Class D units $ 0    
Allocation of net income to general partner:      
Net income 112 352  
Pre-merger net income allocated to general partner interest (2) 0  
Pre-partnership net income allocated to general partner interest 0 (15)  
Net income applicable to noncontrolling interests (23) 0  
Costs charged directly to general partner 20 0  
Income subject to 2% allocation of general partner interest 107 337  
General partner's share of net income 2.00% 2.00%  
General partner's allocated share of net income before items directly allocable to general partner interest 2 7  
Priority allocations, including incentive distributions, paid to general partner 212 153  
Pre-merger net income allocated to general partner interest 2 0  
Pre-partnership net income allocated to general partner interest 0 15  
Costs charged directly to general partner (20) 0  
Net income allocated to general partner's equity 196 175  
Net income 112 352  
Net income allocated to general partner's equity 196 175  
Net income (loss) allocated to Class B limited partners' equity (4) 0  
Net income allocated to Class D limited partners' equity 69 [1] 4 [1]  
Net income applicable to noncontrolling interests 23 0  
Net income (loss) allocated to common limited partners' equity (172) [1] 173 [1]  
ReconciliationAdjustmentsForNetIncomeAllocation [Abstract]      
Incentive distributions paid 212 153  
Incentive distributions declared (212) [2] (158) [2]  
Impact of unit issuance timing 0 (10)  
Allocation of net income (loss) to common units (172) 158  
Distributions Made to Members or Limited Partners [Abstract]      
Per Unit Distribution (Declared) $ 0.85 $ 0.9045  
Subsequent Event [Member]      
Distributions Made to Members or Limited Partners [Abstract]      
Payment Date     May 14, 2015
Per Unit Distribution (Declared)     $ 0.85
Limited Partner [Member] | Class D [Member]      
Amortization of beneficial conversion feature of Class D units 68 5  
Allocation of net income to general partner:      
Net income 1    
Net income $ 1    
[1] The net income allocated to Pre-merger WPZ Class D limited partners includes $68 million and $5 million for the three months ended March 31, 2015 and 2014, respectively, related to the amortization of the beneficial conversion feature associated with the Pre-merger WPZ Class D units.
[2] 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.