Income Taxes - Summary of Tax Effects of Temporary Differences (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Federal foreign tax credit	$ 12.8	$ 7.7
Federal net operating loss carry forward	12.1	0.0
State net operating loss carry forwards	4.3	0.5
Tax basis goodwill and intangibles	149.8	154.1
Depreciation and amortization	61.0	58.2
Deferred restricted common unit compensation	12.1	12.9
Accrued compensation	27.7	28.3
Other	21.7	5.2
Deferred tax assets before valuation allowance	301.5	266.9
Deferred tax assets
Valuation allowance	(21.8)	(14.1)
Total deferred tax assets	279.7	252.8
Deferred tax liabilities
Intangible assets	5.5	7.8
Unrealized appreciation on investments	114.0	126.3
Other	2.4	2.8
Total deferred tax liabilities	121.9	136.9
Net deferred tax assets (liabilities)	$ 157.8	$ 115.9