Consolidating Guarantor and Non-Guarantor Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
CURRENT ASSETS:
Cash and cash equivalents	$ 26,207	$ 12,264	$ 28,176	$ 41,303
Accounts receivable - trade, net of allowance for doubtful accounts	1,072,688	800,607
Accounts receivable-affiliates	4,772	6,711
Inventories	564,553	561,432
Prepaid expenses and other current assets	131,538	103,193
Total current assets	1,799,758	1,484,207
PROPERTY, PLANT AND EQUIPMENT, net of accumulated depreciation	1,719,947	1,790,273
GOODWILL	1,312,558	1,451,716	1,315,362
INTANGIBLE ASSETS, net of accumulated amortization	1,054,482	1,163,956
INVESTMENTS IN UNCONSOLIDATED ENTITIES	17,236	187,423
LOAN RECEIVABLE-AFFILIATE	1,200	3,200
OTHER NONCURRENT ASSETS	245,941	239,604
Total assets	6,151,122	6,320,379
CURRENT LIABILITIES:
Accounts payable-trade	860,629	658,021
Accounts payable-affiliates	1,254	7,918
Accrued expenses and other payables	230,087	207,125
Advance payments received from customers	21,216	35,944
Current maturities of long-term debt	3,196	29,590
Total current liabilities	1,116,382	938,598
LONG-TERM DEBT, net of debt issuance costs and current maturities	2,682,628	2,963,483
OTHER NONCURRENT LIABILITIES	173,514	184,534
CLASS A 10.75% CONVERTIBLE PREFERRED UNITS	82,576	63,890
REDEEMABLE NONCONTROLLING INTEREST	9,927	3,072
EQUITY:
Partners' equity	2,004,407	2,141,884
Accumulated other comprehensive income (loss)	(1,815)	(1,828)
Noncontrolling interests	83,503	26,746
Total equity	2,086,095	2,166,802	1,694,065	2,693,432
Total liabilities and equity	6,151,122	6,320,379
Reportable Entity
CURRENT ASSETS:
Cash and cash equivalents			25,749
Reportable Entity | NGL Energy Partners LP (Parent)
CURRENT ASSETS:
Cash and cash equivalents	16,915	6,257	25,749	29,115
Total current assets	16,915	6,257
INTANGIBLE ASSETS, net of accumulated amortization	0	0
NET INTERCOMPANY RECEIVABLES (PAYABLES)	2,110,940	2,424,730
INVESTMENTS IN CONSOLIDATED SUBSIDIARIES	1,703,327	1,978,158
Total assets	3,831,182	4,409,145
CURRENT LIABILITIES:
Accounts payable-affiliates	1	1
Accrued expenses and other payables	41,104	42,150
Current maturities of long-term debt	0	25,000
Total current liabilities	41,105	67,151
LONG-TERM DEBT, net of debt issuance costs and current maturities	1,704,909	2,138,048
CLASS A 10.75% CONVERTIBLE PREFERRED UNITS	82,576	63,890
EQUITY:
Partners' equity	2,002,592	2,140,056
Total equity	2,002,592	2,140,056
Total liabilities and equity	3,831,182	4,409,145
Reportable Entity | Guarantor Subsidiaries
CURRENT ASSETS:
Cash and cash equivalents	6,083	2,903	784	9,757
Accounts receivable - trade, net of allowance for doubtful accounts	1,064,266	795,479
Accounts receivable-affiliates	4,772	6,711
Inventories	563,475	560,769
Prepaid expenses and other current assets	130,968	102,703
Total current assets	1,769,564	1,468,565
PROPERTY, PLANT AND EQUIPMENT, net of accumulated depreciation	1,560,245	1,725,383
GOODWILL	1,233,581	1,437,759
INTANGIBLE ASSETS, net of accumulated amortization	963,806	1,149,524
INVESTMENTS IN UNCONSOLIDATED ENTITIES	17,236	187,423
NET INTERCOMPANY RECEIVABLES (PAYABLES)	(2,121,742)	(2,408,189)
INVESTMENTS IN CONSOLIDATED SUBSIDIARIES	244,109	47,598
LOAN RECEIVABLE-AFFILIATE	1,200	3,200
OTHER NONCURRENT ASSETS	245,941	239,436
Total assets	3,913,940	3,850,699
CURRENT LIABILITIES:
Accounts payable-trade	858,000	657,077
Accounts payable-affiliates	1,253	7,907
Accrued expenses and other payables	187,327	164,012
Advance payments received from customers	16,664	35,107
Current maturities of long-term debt	2,819	4,211
Total current liabilities	1,066,063	868,314
LONG-TERM DEBT, net of debt issuance costs and current maturities	976,962	824,370
OTHER NONCURRENT LIABILITIES	167,588	179,857
REDEEMABLE NONCONTROLLING INTEREST	0	0
EQUITY:
Partners' equity	1,704,896	1,979,785
Accumulated other comprehensive income (loss)	(1,569)	(1,627)
Noncontrolling interests	0
Total equity	1,703,327	1,978,158
Total liabilities and equity	3,913,940	3,850,699
Reportable Entity | Non-Guarantor Subsidiaries
CURRENT ASSETS:
Cash and cash equivalents	3,209	3,104	$ 1,643	$ 2,431
Accounts receivable - trade, net of allowance for doubtful accounts	8,422	5,128
Accounts receivable-affiliates	0	0
Inventories	1,078	663
Prepaid expenses and other current assets	570	490
Total current assets	13,279	9,385
PROPERTY, PLANT AND EQUIPMENT, net of accumulated depreciation	159,702	64,890
GOODWILL	78,977	13,957
INTANGIBLE ASSETS, net of accumulated amortization	90,676	14,432
INVESTMENTS IN UNCONSOLIDATED ENTITIES	0	0
NET INTERCOMPANY RECEIVABLES (PAYABLES)	10,802	(16,541)
OTHER NONCURRENT ASSETS	0	168
Total assets	353,436	86,291
CURRENT LIABILITIES:
Accounts payable-trade	2,629	944
Accounts payable-affiliates	0	10
Accrued expenses and other payables	1,656	963
Advance payments received from customers	4,552	837
Current maturities of long-term debt	377	379
Total current liabilities	9,214	3,133
LONG-TERM DEBT, net of debt issuance costs and current maturities	757	1,065
OTHER NONCURRENT LIABILITIES	5,926	4,677
REDEEMABLE NONCONTROLLING INTEREST	9,927	3,072
EQUITY:
Partners' equity	327,858	74,545
Accumulated other comprehensive income (loss)	(246)	(201)
Total equity	327,612	74,344
Total liabilities and equity	353,436	86,291
Consolidating Adjustments
CURRENT ASSETS:
INVESTMENTS IN CONSOLIDATED SUBSIDIARIES	(1,947,436)	(2,025,756)
Total assets	(1,947,436)	(2,025,756)
EQUITY:
Partners' equity	(2,030,939)	(2,052,502)
Noncontrolling interests	83,503	26,746
Total equity	(1,947,436)	(2,025,756)
Total liabilities and equity	$ (1,947,436)	$ (2,025,756)