Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jan. 15, 2021	Jan. 04, 2021	Dec. 15, 2020	Dec. 01, 2020	Nov. 13, 2020	Oct. 30, 2020	Oct. 16, 2020	Sep. 15, 2020	Jul. 15, 2020	Jun. 15, 2020	Apr. 15, 2020	Mar. 16, 2020	Jan. 15, 2020	Dec. 16, 2019	Oct. 15, 2019	Sep. 16, 2019	Jul. 15, 2019	Jun. 17, 2019	Apr. 15, 2019	Mar. 15, 2019	Jan. 15, 2019	Sep. 30, 2020
Subsequent Event [Line Items]
Restructuring and Related Cost, Number of Positions Eliminated, Inception to Date Percent																						15.00%
Restructuring and Related Cost, Expected Cost																						$ 9
Series A Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Preferred Limited Partnership Unit; Distribution Amount Declared										$ 36.875				$ 36.875				$ 36.875
Series B Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Preferred Limited Partnership Unit; Distribution Amount Declared								$ 0.4922		$ 0.4922		$ 0.4922		$ 0.4922		$ 0.4922		$ 0.4922		$ 0.4922
Series C Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Preferred Limited Partnership Unit; Distribution Amount Declared									$ 0.4969		$ 0.4969		$ 0.4969		$ 0.4969		$ 0.4969		$ 0.4969		$ 0.5576
Subsequent Event [Member]
Subsequent Event [Line Items]
Distribution Made to Limited Partner, Distributions Declared, Per Unit							$ 0.39
Distribution Made to Common Unitholders, Declaration Date							Oct. 16, 2020
Distribution Made to Limited Partner, Date of Record						Oct. 30, 2020
Distribution Made to Limited Partner, Distribution Date					Nov. 13, 2020
Subsequent Event [Member] | Series A Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Preferred Limited Partner Distribution: Record Date				Dec. 01, 2020
Preferred Limited Partnership Distribution; Distribution Date			Dec. 15, 2020
Preferred Limited Partnership Unit; Distribution Amount Declared							$ 36.875
Subsequent Event [Member] | Series B Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Distribution Made to Common Unitholders, Declaration Date							Oct. 16, 2020
Preferred Limited Partner Distribution: Record Date				Dec. 01, 2020
Preferred Limited Partnership Distribution; Distribution Date			Dec. 15, 2020
Preferred Limited Partnership Unit; Distribution Amount Declared							$ 0.4922
Subsequent Event [Member] | Series C Preferred Limited Partners [Member]
Subsequent Event [Line Items]
Distribution Made to Common Unitholders, Declaration Date							Oct. 16, 2020
Preferred Limited Partner Distribution: Record Date		Jan. 04, 2021
Preferred Limited Partnership Distribution; Distribution Date	Jan. 15, 2021
Preferred Limited Partnership Unit; Distribution Amount Declared							$ 0.4969