Operating Expenses - Components of Operating Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Income and Expenses [Abstract]
Fixed compensation expense									$ 35,093	$ 29,057	$ 23,248
Variable compensation expense									12,606	14,863	22,245
Equity compensation expense									11,921	9,750	10,077
Total compensation expense									59,620	53,670	55,570
Systems and consulting									10,212	11,654	7,517
Loan acquisition costs									10,326	8,207	7,605
Accounting and legal									4,837	5,244	6,263
Office costs									5,270	5,011	3,503
Corporate costs									2,049	2,237	2,721
Other operating expenses									5,102	4,100	3,428
Total Operating Expenses	$ 22,638	$ 24,497	$ 25,218	$ 25,063	$ 26,462	$ 21,406	$ 22,282	$ 19,973	$ 97,416	$ 90,123	86,607
Severance expense											$ 4,000