Income Taxes - Summary of Tax Effects of Temporary Differences (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Federal foreign tax credit	$ 7.7	$ 3.8
State net operating loss carry forwards	0.5	3.6
Tax basis goodwill and intangibles	154.1	99.4
Depreciation and amortization	58.2	38.6
Deferred restricted common unit compensation	12.9	12.6
Accrued compensation	28.3	37.6
Other	5.2	0.6
Deferred tax assets before valuation allowance	266.9	196.2
Deferred tax assets
Valuation allowance	(14.1)	(29.7)
Total deferred tax assets	252.8	166.5
Deferred tax liabilities
Intangible assets	7.8	19.4
Unrealized appreciation on investments	126.3	126.3
Other	2.8	2.0
Total deferred tax liabilities	136.9	147.7
Net deferred tax assets (liabilities)	$ 115.9	$ 18.8