Other Indebtedness - Schedule of Terms and Principal Amounts of Each Debt Instrument (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Other indebtedness	$ 182.5	$ 55.4	[1]
Term Loan [Member]
Debt Instrument [Line Items]
Other indebtedness	125.0	0.0
Floating Rate Loan Stock [Member]
Debt Instrument [Line Items]
Other indebtedness	56.9	54.8
Other Debt [Member]
Debt Instrument [Line Items]
Other indebtedness	$ 0.6	$ 0.6

[1] Derived from audited consolidated financial statements.