Carrying Values and Estimated Fair Values of Consolidated Financial Instruments (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Assets
Investments (excluding equity method investments and loans)	[1]	$ 19,051.9	$ 17,632.3
Liabilities
Senior Notes and other debt	[2]	2,468.7	1,962.7
Carrying Value
Assets
Investments (excluding equity method investments and loans)	[1]	19,051.9	17,632.3
Liabilities
Senior Notes and other debt	[2]	$ 2,135.9	$ 1,751.1

[1] This table includes debt and equity securities, as well as partnership and non-marketable equity investments accounted for at fair value that are included in other invested assets. This table excludes investments accounted for using the equity method and commercial mortgage loans that are accounted for at unpaid principal balance. The fair value of short-term investments approximates amortized cost.

[2] See Note 8 for additional information on the Senior Notes and other debt.