Aggregate Positions in Capital Structure of Borrowers (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt, total	$ 488,508	$ 166,464
First Lien [Member]
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt, total	280,441
Second Lien [Member]
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt, total	133,385
Corporate Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Corporate debt, total	$ 74,682