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Debt and Interest Expense - Debt Outstanding Table (Details) - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Short-term debt, carrying value $ 28,000,000 $ 0
Total long-term debt, principal 4,220,000,000 3,518,000,000
Long-term debt, carrying value 4,176,346,000 3,492,712,000
Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 4,244,116,000 3,622,177,000
WGP RCF [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Principal 28,000,000 28,000,000
Short-term debt, carrying value 28,000,000  
Long-term debt, carrying value   28,000,000
WGP RCF [Member] | Revolving Credit Facility [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Short-term debt, fair value [1] 28,000,000  
Long-term debt, fair value [1]   28,000,000
Western Gas Partners, LP [Member] | WES RCF [Member] | Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Principal 0 370,000,000
Long-term debt, carrying value 0 370,000,000
Western Gas Partners, LP [Member] | WES RCF [Member] | Revolving Credit Facility [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 0 370,000,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 2.600% Senior Notes due 2018 [Member]    
Debt Instrument [Line Items]    
Principal 350,000,000 350,000,000
Long-term debt, carrying value 349,810,000 349,684,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 2.600% Senior Notes due 2018 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 349,542,000 350,631,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member]    
Debt Instrument [Line Items]    
Principal 500,000,000 500,000,000
Long-term debt, carrying value 496,095,000 495,815,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.375% Senior Notes due 2021 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 522,069,000 530,647,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member]    
Debt Instrument [Line Items]    
Principal 670,000,000 670,000,000
Long-term debt, carrying value 668,906,000 668,849,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.000% Senior Notes due 2022 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 670,857,000 684,043,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 3.950% Senior Notes due 2025 [Member]    
Debt Instrument [Line Items]    
Principal 500,000,000 500,000,000
Long-term debt, carrying value 492,120,000 491,885,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 3.950% Senior Notes due 2025 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 487,240,000 500,885,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.650% Senior Notes due 2026 [Member]    
Debt Instrument [Line Items]    
Principal 500,000,000 500,000,000
Long-term debt, carrying value 495,360,000 495,245,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.650% Senior Notes due 2026 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 508,551,000 520,144,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.500% Senior Notes due 2028 [Member]    
Debt Instrument [Line Items]    
Principal 400,000,000 0
Long-term debt, carrying value 394,285,000 0
Western Gas Partners, LP [Member] | Senior Notes [Member] | 4.500% Senior Notes due 2028 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 401,807,000 0
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member]    
Debt Instrument [Line Items]    
Principal 600,000,000 600,000,000
Long-term debt, carrying value 593,262,000 593,234,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.450% Senior Notes due 2044 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] 605,816,000 637,827,000
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.300% Senior Notes due 2048 [Member]    
Debt Instrument [Line Items]    
Principal 700,000,000 0
Long-term debt, carrying value 686,508,000 0
Western Gas Partners, LP [Member] | Senior Notes [Member] | 5.300% Senior Notes due 2048 [Member] | Market Approach Valuation Technique [Member] | Level 2 Inputs [Member]    
Debt Instrument [Line Items]    
Long-term debt, fair value [1] $ 698,234,000 $ 0
[1] Fair value is measured using the market approach and Level 2 inputs.