Partnership's Repurchase Activities (Detail) - $ / shares shares in Thousands		3 Months Ended				12 Months Ended		48 Months Ended
		Sep. 30, 2016		Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2016		Sep. 30, 2015		Jun. 30, 2016
Capital Unit [Line Items]
Partnership's common units authorized for repurchase		7,344				7,344
Private Transaction
Capital Unit [Line Items]
Partnership's common units authorized for repurchase		2,450				2,450
Total Number of Units Purchased		1,300						1,150
Plan III Common Units Repurchase Program
Capital Unit [Line Items]
Partnership's common units authorized for repurchase		4,894				4,894
Total Number of Units Purchased	[2]	1,300	[1]	92	3	1,395		3,742	[3]
Average Price Paid per Unit	[4]	$ 8.70	[1]	$ 7.49	$ 7.02	$ 8.62		$ 4.72	[3]
Maximum Number of Units that May Yet Be Purchased		2,207	[1]	2,207	2,299	2,207	[1]	2,302	[3]	2,207

[1] Includes 1.3 million common units acquired in a private transaction.

[2] Units were repurchased as part of a publicly announced program, except as noted in a private transaction.

[3] Includes 1.15 million common units acquired in a private transaction.

[4] Amounts include repurchase costs.