Basis of Presentation and Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents		$ 273.4	$ 317.5
Restricted cash - current	[1]	28.0	18.1
Restricted cash - noncurrent	[2]	0.1	0.3
Total cash, cash equivalents and restricted cash		$ 301.5	$ 335.9

[1] Included within prepaid expenses and other current assets within the Consolidated Balance Sheets.

[2] Included within other noncurrent assets within the Consolidated Balance Sheets.