Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)		3 Months Ended	12 Months Ended
		Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3			$ 22,900,000	$ 253,800,000
Gross transfers into Level 3			19,900,000	58,400,000
Ares
Fair Value Disclosures [Line Items]
Gain (loss) on conversion of private equity interests into limited partnership interests		$ 0
Debt Securities
Fair Value Disclosures [Line Items]
Gross transfers into Level 3				58,400,000
Debt Securities | U.S. corporate bonds
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3			15,900,000	14,700,000
Gross transfers into Level 3			14,200,000	23,200,000
Debt Securities | Foreign corporate bonds
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3			5,500,000	1,000,000
Gross transfers into Level 3			700,000	6,100,000
Debt Securities | Mortgage and asset backed securities | Other asset-backed securities
Fair Value Disclosures [Line Items]
Gross transfers into Level 3				29,100,000
Debt Securities | Mortgage and asset backed securities | Other asset-backed securities | Collateralized loan obligations
Fair Value Disclosures [Line Items]
Gross transfers into Level 3				29,100,000
Other invested assets
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3	[1]		1,500,000	238,100,000
Gross transfers into Level 3	[1]		$ 5,000,000
Other invested assets | Ares
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3		$ 232,900,000
All Other
Fair Value Disclosures [Line Items]
Gross transfers out of Level 3				$ 20,900,000

[1] Includes partnership and non-marketable equity investments accounted for on an AFS basis.