Clawback Obligations by Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Product Liability Contingency [Line Items]
Clawback obligations	$ 2,172	$ 2,171
Credit Segment
Product Liability Contingency [Line Items]
Clawback obligations	2,172	2,171
Credit Segment | Blackstone Holdings
Product Liability Contingency [Line Items]
Clawback obligations	1,059	1,059
Credit Segment | Current And Former Blackstone Personnel
Product Liability Contingency [Line Items]
Clawback obligations	$ 1,113	$ 1,112