Unaudited Condensed Consolidated Statement of Changes in Equity - 6 months ended Sep. 30, 2018 - USD ($)	Total	Accumulated other comprehensive (loss) income	Noncontrolling Interests	General Partner	Class B Perpetual Preferred Units	Class B Perpetual Preferred Units Class B Perpetual Preferred Units	Limited Partner	Limited Partner Common units
Beginning Balance (in units) at Mar. 31, 2018						8,400,000		121,472,725
Beginning Balance at Mar. 31, 2018	$ 2,086,095,000	$ (1,815,000)	$ 83,503,000	$ (50,819,000)	$ 202,731,000		$ 1,852,495,000
Increase (Decrease) in Partnership Capital
Distributions to general and common unit partners and preferred unitholders (Note 10)	(117,486,000)			(164,000)			(117,322,000)
Contributions	169,000		169,000
Sawtooth joint venture	0		63,000				(63,000)
Purchase of noncontrolling interest (Note 4)	(3,960,000)		(3,927,000)				(33,000)
Redeemable noncontrolling interest valuation adjustment (Note 2)	(3,349,000)						(3,349,000)
Repurchase of warrants	(14,988,000)						(14,988,000)
Equity issued pursuant to incentive compensation plan (in units)								2,044,601
Equity issued pursuant to incentive compensation plan (Note 10)	27,393,000			21,000			27,372,000
Common unit repurchases and cancellations (in units)								(4,661)
Common unit repurchases and cancellations (Note 10)	(54,000)						(54,000)
Warrants exercised (in units)								228,797
Warrants exercised (Note 10)	2,000						2,000
Accretion of beneficial conversion feature of Class A convertible preferred units (Note 10)	(21,786,000)						(21,786,000)
Preferred units, issued (in units)						8,400,000
Preferred units issued, net of offering costs					202,700,000
Net income (loss)	186,096,000		(863,000)	212,000			186,747,000
Other comprehensive loss	(24,000.000)	(24,000)
Ending Balance (in units) at Sep. 30, 2018						8,400,000		123,741,462
Ending Balance at Sep. 30, 2018	2,277,414,000	(270,000)	$ 78,945,000	(50,613,000)	$ 202,731,000		2,046,621,000
Increase (Decrease) in Partnership Capital
Cumulative effect adjustment for adoption of ASC 606 (Note 15)	139,306,000
Cumulative effect adjustment for adoption of ASC 606 (Note 15) | General Partner Interest in TLP				139,000			139,167,000
Cumulative effect adjustment for adoption of ASU 2016-01 (Note 2)	$ 0
Cumulative effect adjustment for adoption of ASU 2016-01 (Note 2) | Available-for-sale securities		$ 1,569,000		$ (2,000)			$ (1,567,000)