Partnership Capital - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017	Jan. 12, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 17, 2014
Partners Capital Account [Line Items]
Period of loans made by Partnership to general partners	1 year
Outstanding amount of partner loans financed through the Partnership	$ 381	$ 335		$ 297	$ 266
Interest income from outstanding amount of general partner loan	$ 4	$ 3
Limited partnership's minimum annual payment rate	7.50%	7.50%
Limited partnership's minimum return, value	$ 17	$ 17
2014 Limited Partnership Offering [Member]
Partners Capital Account [Line Items]
Limited partnership amount registered						$ 350
Limited partnership interests issued	298
Remaining limited partnership interests that may be issued	$ 52
2018 Limited Partnership Offering [Member]
Partners Capital Account [Line Items]
Limited partnership amount registered			$ 450