Components of Operating Expenses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Component of Operating Other Cost and Expense [Abstract]
Fixed compensation expense	$ 6,872	$ 6,080	$ 13,664	$ 11,716
Variable compensation expense	3,021	3,960	5,752	8,797
Equity compensation expense	2,824	3,396	5,154	5,883
Severance expense	222	3,366	222	3,434
Total compensation expense	12,939	16,802	24,792	29,830
Systems and consulting	3,977	2,318	7,443	4,060
Accounting and legal	1,183	805	2,816	3,052
Office costs	1,170	827	2,155	1,615
Corporate costs	558	528	1,111	1,037
Other operating expenses	2,455	3,150	3,937	5,022
Total Operating Expenses	$ 22,282	$ 24,430	$ 42,254	$ 44,616