Borrowings - Partnership's Borrowings (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Borrowings [Line Items]
Borrowing Outstanding	$ 1,138.7	$ 1,140.2
Carrying Value	1,145.1	1,146.9
Senior Credit Facility Term Loan Due 5/05/2020
Borrowings [Line Items]
Borrowing Outstanding	25.0	25.0
Carrying Value	25.0	25.0
CLO Term Loan
Borrowings [Line Items]
Borrowing Outstanding	13.7	15.2
Carrying Value	13.7	15.2
3.875% senior notes due 2023
Borrowings [Line Items]
Borrowing Outstanding	500.0	500.0
Carrying Value	499.9	499.9
5.625% senior notes due 2043
Borrowings [Line Items]
Borrowing Outstanding	600.0	600.0
Carrying Value	$ 606.5	$ 606.8