Commitments And Contingencies - Additional Information (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2016
Commitments and Contingencies [Line Items]
Commitment to purchase alternative investment		$ 40,000,000		$ 50,000,000	$ 40,000,000
Future Funding Commitments		24,768,000	$ 20,014,000
Rental expense under operating leases, net of sub-lease income		3,700,000	3,500,000	2,600,000
Rental expense under operating leases, sub-lease income		20,000	70,000	$ 40,000
European Non-Performing Loan Fund, LP
Commitments and Contingencies [Line Items]
Funded commitment amount		34,300,000
Future Funding Commitments	[1]	15,714,000	$ 20,014,000
Private Middle Market Loans, LLC
Commitments and Contingencies [Line Items]
Funded commitment amount		30,900,000
Future Funding Commitments	[2]	9,054,000
Unfunded Commitments | European Non-Performing Loan Fund, LP
Commitments and Contingencies [Line Items]
Future Funding Commitments		15,700,000
Unfunded Commitments | Private Middle Market Loans, LLC
Commitments and Contingencies [Line Items]
Future Funding Commitments		$ 9,100,000

[1] This limited partnership invests in distressed securities and assets through senior and subordinated, secured and unsecured debt and equity, in both public and private large-cap and middle-market companies. The Company does not have the ability to sell or transfer its limited partnership interest without consent from the general partner. The Company does not have the contractual option to redeem its limited partnership interest but receives distributions based on the liquidation of the underlying assets. Based on the terms of the partnership agreement, the Company anticipates its interest in this partnership to be redeemed by 2020.

[2] This limited partnership provides financing for middle market companies. The Company does not have the ability to sell or transfer its limited partnership interest without consent from the general partner. The Company does not have the contractual option to redeem its limited partnership interest but receives distributions based on the liquidation of the underlying assets. Based on the terms of the investment management agreement, the Company anticipates its interest to be redeemed no later than 2024.