Supplemental Cash Flow Information - Reconciliation of Total Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Condensed Cash Flow Statements Captions [Line Items]
Cash and cash equivalents	$ 18.4	$ 27.2	$ 40.2
Cash and cash equivalents—discontinued operations			0.1
Cash, cash equivalents, restricted cash and restricted cash equivalents, end of period	24.7	$ 32.7	43.9	$ 43.3
Prepaid Expenses, Supplies, and Other Current Assets
Condensed Cash Flow Statements Captions [Line Items]
Restricted cash and restricted cash equivalents	2.1
Other Noncurrent Assets
Condensed Cash Flow Statements Captions [Line Items]
Restricted cash and restricted cash equivalents	$ 4.2		$ 3.6