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Debt and Interest Expense - Debt Outstanding Table (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 13, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Finance leases - short-term debt	$ 8,264		$ 7,873
Total short-term debt, principal	439,345		7,873
Total short-term debt, carrying value	438,870		7,873
Finance lease liabilities	23,644		0
Long-term debt	7,415,832		7,951,565
Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Short-term debt, fair value	444,505		7,873
Long-Term Debt Obligations [Member]
Debt Instrument [Line Items]
Total long-term debt, principal	7,494,539		8,000,000
Long-term debt	7,415,832		7,951,565
Long-Term Debt Obligations [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	7,845,524		7,849,818
WES Operating [Member]
Debt Instrument [Line Items]
Total short-term debt, carrying value	438,870		7,873
Long-term debt	7,415,832		7,951,565
WES Operating [Member] \| Finance Lease Liability, Short Term [Member]
Debt Instrument [Line Items]
Finance leases - short-term debt	8,264		7,873
WES Operating [Member] \| Finance Lease Liability, Short Term [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Finance leases - short-term debt	8,264		7,873
WES Operating [Member] \| RCF [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal	0		380,000
Long-term debt, carrying value	0		380,000
WES Operating [Member] \| RCF [Member] \| Revolving Credit Facility [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	0		380,000
WES Operating [Member] \| Term Loan Facility [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal	0		3,000,000
Long-term debt, carrying value	0		3,000,000
WES Operating [Member] \| Term Loan Facility [Member] \| Revolving Credit Facility [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	0		3,000,000
WES Operating [Member] \| Finance Lease Liability, Long Term [Member]
Debt Instrument [Line Items]
Finance lease liabilities	23,644		0
WES Operating [Member] \| Finance Lease Liability, Long Term [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Finance lease liabilities	$ 23,644		0
WES Operating [Member] \| Senior Notes [Member] \| 5.375% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	5.375%
Principal	$ 431,081		500,000
Short-term debt, carrying value	430,606
Long-term debt, carrying value			498,168
WES Operating [Member] \| Senior Notes [Member] \| 5.375% Senior Notes due 2021 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Short-term debt, fair value	$ 436,241
Long-term debt, fair value			515,042
WES Operating [Member] \| Senior Notes [Member] \| 4.000% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	4.00%
Principal	$ 580,917		670,000
Long-term debt, carrying value	580,555		669,322
WES Operating [Member] \| Senior Notes [Member] \| 4.000% Senior Notes due 2022 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	597,568		689,784
WES Operating [Member] \| Senior Notes [Member] \| Floating-Rate Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Principal	239,978		0
Long-term debt, carrying value	238,879		0
WES Operating [Member] \| Senior Notes [Member] \| Floating-Rate Senior Notes due 2023 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 235,066		0
WES Operating [Member] \| Senior Notes [Member] \| 3.100% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	3.10%	3.10%
Principal	$ 1,000,000		0
Long-term debt, carrying value	992,900		0
WES Operating [Member] \| Senior Notes [Member] \| 3.100% Senior Notes due 2025 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 1,028,614		0
WES Operating [Member] \| Senior Notes [Member] \| 3.950% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	3.95%
Principal	$ 500,000		500,000
Long-term debt, carrying value	494,866		493,830
WES Operating [Member] \| Senior Notes [Member] \| 3.950% Senior Notes due 2025 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 512,807		504,968
WES Operating [Member] \| Senior Notes [Member] \| 4.650% Senior Notes due 2026 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	4.65%
Principal	$ 500,000		500,000
Long-term debt, carrying value	496,708		496,197
WES Operating [Member] \| Senior Notes [Member] \| 4.650% Senior Notes due 2026 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 524,880		513,393
WES Operating [Member] \| Senior Notes [Member] \| 4.500% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	4.50%
Principal	$ 400,000		400,000
Long-term debt, carrying value	395,617		395,113
WES Operating [Member] \| Senior Notes [Member] \| 4.500% Senior Notes due 2028 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 415,454		390,920
WES Operating [Member] \| Senior Notes [Member] \| 4.750% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	4.75%
Principal	$ 400,000		400,000
Long-term debt, carrying value	396,555		396,190
WES Operating [Member] \| Senior Notes [Member] \| 4.750% Senior Notes due 2028 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 418,786		400,962
WES Operating [Member] \| Senior Notes [Member] \| 4.050% Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	4.05%	4.05%
Principal	$ 1,200,000		0
Long-term debt, carrying value	1,189,407		0
WES Operating [Member] \| Senior Notes [Member] \| 4.050% Senior Notes due 2030 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 1,342,996		0
WES Operating [Member] \| Senior Notes [Member] \| 5.450% Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	5.45%
Principal	$ 600,000		600,000
Long-term debt, carrying value	593,598		593,470
WES Operating [Member] \| Senior Notes [Member] \| 5.450% Senior Notes due 2044 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 607,234		533,710
WES Operating [Member] \| Senior Notes [Member] \| 5.300% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	5.30%
Principal	$ 700,000		700,000
Long-term debt, carrying value	687,048		686,843
WES Operating [Member] \| Senior Notes [Member] \| 5.300% Senior Notes due 2048 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 694,172		610,841
WES Operating [Member] \| Senior Notes [Member] \| 5.500% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	5.50%
Principal	$ 350,000		350,000
Long-term debt, carrying value	342,543		342,432
WES Operating [Member] \| Senior Notes [Member] \| 5.500% Senior Notes due 2048 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 343,928		310,198
WES Operating [Member] \| Senior Notes [Member] \| 5.250% Senior Notes due 2050 [Member]
Debt Instrument [Line Items]
Senior note, interest rate	5.25%	5.25%
Principal	$ 1,000,000		0
Long-term debt, carrying value	983,512		0
WES Operating [Member] \| Senior Notes [Member] \| 5.250% Senior Notes due 2050 [Member] \| Valuation, Market Approach [Member] \| Level-2 Inputs [Member]
Debt Instrument [Line Items]
Long-term debt, fair value	$ 1,100,375		$ 0