Offsetting of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	$ 88,985	$ 3,813
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	86,504	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received, Assets	826	352
Net Amount, Assets	1,655	2,329
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	66,896	38,560
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	43,109	30,570
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	18,149	7,893
Net Amount, Liabilities	5,638	97
Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	42,102	29,907
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	41,433	29,438
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	669	469
Net Amount, Liabilities	0
Freestanding Derivatives
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	3,703	3,290
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	1,676	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received, Assets	826	352
Net Amount, Assets	1,201	1,806
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	24,550	8,653
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	1,676	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	17,480	7,424
Net Amount, Liabilities	5,394	97
Reverse Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	85,282
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	84,828
Net Amount, Assets	$ 454
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition		523
Net Amount, Assets		$ 523