Offsetting of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	$ 10,825	$ 124,215
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	2,464	118,839
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received		2,892
Net Amount	8,361	2,484
Repurchase agreements gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	74,728	75,324
Repurchase agreements gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	74,728	72,195
Repurchase agreements gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received		3,129
Repurchase agreements Net Amount	0	0
Gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	86,531	82,797
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	77,192	73,259
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received	8,503	8,767
Net Amount	836	771
Reverse repurchase agreements gross and Net Amounts of Assets Presented in the Statement of Financial Condition		118,495
Reverse repurchase agreements gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments		117,775
Reverse repurchase agreements gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received		0
Reverse repurchase agreements Net Amount		720
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Derivatives gross and Net Amounts of Assets Presented in the Statement of Financial Condition	29
Derivatives Net Amount	29
Derivatives gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition		587
Derivatives Net Amount		587
Freestanding Derivatives
Offsetting Assets and Liabilities [Line Items]
Derivatives gross and Net Amounts of Assets Presented in the Statement of Financial Condition	10,796	5,720
Derivatives gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	2,464	1,064
Derivatives gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received		2,892
Derivatives Net Amount	8,332	1,764
Derivatives gross and Net Amounts of Liabilities Presented in the Statement of Financial Condition	11,803	6,886
Derivatives gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	2,464	1,064
Derivatives gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received	8,503	5,638
Derivatives Net Amount	$ 836	$ 184