Long-Term Debt - Credit Agreement (Details) $ in Thousands		3 Months Ended
	Jul. 05, 2018	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Long-Term Debt
Face amount		$ 3,052,369	$ 2,701,031
LONG-TERM DEBT, debt issuance costs		19,340	20,645
Debt and Capital Lease Obligations		3,033,029	2,680,386
Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity		$ 1,765,000
Financial Covenants in Credit Agreement
Debt Instrument, actual leverage ratio		4.50
Debt Instrument, actual senior secured leverage ratio		0.61
Debt Instrument, actual interest coverage ratio		2.71
Revolving Credit Facility | Minimum
Long-Term Debt
Commitment fees charged on unused capacity		0.375%
Financial Covenants in Credit Agreement
Debt instrument, covenant interest coverage ratio June 30, 2018 to December 31, 2018		2.50
Debt instrument, covenant Interest coverage ratio December 31, 2018 to March 31, 2019		2.75
Debt instrument, covenant interest coverage ratio March 31, 2019 to October 5, 2021		2.75
Revolving Credit Facility | Maximum
Long-Term Debt
Commitment fees charged on unused capacity		0.50%
Financial Covenants in Credit Agreement
Debt instrument, covenant leverage ratio June 30, 2018 to March 31, 2019		4.75
Debt instrument, covenant leverage ratio March 31, 2019 to October 5, 2021		4.50
Debt instrument, covenant senior secured leverage ratio June 30, 2018 to October 5, 2021		3.25
Debt instrument, total leverage indebtedness ratio March 31, 2019 to October 5, 2021		6.50
Revolving Credit Facility | LIBOR option
Long-Term Debt
Interest rate margin added to variable rate base		2.50%
Reference rate		2.09%
Revolving Credit Facility | Prime rate
Long-Term Debt
Interest rate margin added to variable rate base		1.50%
Reference rate		5.00%
Revolving Credit Facility
Long-Term Debt
Interest rate		4.79%
Working Capital Facility | Revolving Credit Facility
Long-Term Debt
Face amount		$ 1,060,500	969,500
LONG-TERM DEBT, debt issuance costs		0	0
Debt and Capital Lease Obligations		1,060,500	969,500
Maximum borrowing capacity		1,300,000
Working Capital Facility | Letter of Credit
Long-Term Debt
Outstanding letters of credit		128,400
Expansion Capital Facility | Revolving Credit Facility
Long-Term Debt
Face amount		265,500	0
LONG-TERM DEBT, debt issuance costs		0	0
Debt and Capital Lease Obligations		265,500	$ 0
Maximum borrowing capacity		$ 465,000
Letter of Credit | Revolving Credit Facility
Long-Term Debt
Fixed interest rate		2.50%
Subsequent Event | Revolving Credit Facility
Long-Term Debt
Credit agreement change to guarantors	In the amendment, the lenders consented to, subject to the consummation of the Retail Propane disposition, release Retail Propane, LLC and its wholly-owned subsidiaries from its guaranty and other obligations under the loan documents. In return, the Partnership agreed to use the net proceeds from the Retail Propane disposition to pay down existing indebtedness no later than five business days after the consummation of the Retail Propane disposition.