Goodwill and Other Intangibles - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		$ 8.8	$ 10.9	$ 19.5
Estimated future amortization expense for 2017		8.8
Estimated future amortization expense for 2018		8.1
Estimated future amortization expense for 2019		8.0
Estimated future amortization expense for 2020		7.9
Estimated future amortization expense for 2021		5.7
Goodwill		519.4	526.4	533.2
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		$ 8.8	$ 10.9	$ 19.5
Aviate Global LLP
Acquired Finite-Lived Intangible Assets [Line Items]
Performance related adjustment period	3 years
Purchase price	$ 18.8
Goodwill	11.8
Intangible assets acquired	$ 4.5