Offsetting of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	$ 66,531	$ 3,813
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	63,131	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received, Assets	659	352
Net Amount, Assets	2,741	2,329
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	53,957	38,560
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	42,964	30,570
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	10,980	7,893
Net Amount, Liabilities	13	97
Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	41,654	29,907
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	40,983	29,438
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	671	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	4,630	3,290
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	1,981	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received, Assets	659	352
Net Amount, Assets	1,990	1,806
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	12,303	8,653
Gross Amount Not Offset in the Statement of Financial Condition, Financial Instruments, Liabilities	1,981	1,132
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Pledged, Liabilities	10,309	7,424
Net Amount, Liabilities	13	97
Reverse Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	61,376
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments, Assets	61,150
Net Amount, Assets	226
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	525	523
Net Amount, Assets	$ 525	$ 523