Offsetting of Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	$ 159,327	$ 303,362
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	151,419	252,001
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received	582	36,748
Asset Net Amount	7,326	14,613
Gross And Net Amounts Of Liabilities Presented In the Statement Of Financial Condition	320,634	146,463
Gross Amount of Liabilities Not Offset in the Statement of Financial Condition, Financial Instruments	319,377	146,249
Cash Collateral Pledged	1,257
Liability Net Amount		214
Freestanding Derivatives
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	10,343	55,344
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	3,025	3,983
Gross Amounts Not Offset in the Statement of Financial Condition, Cash Collateral Received	582	36,748
Asset Net Amount	6,736	14,613
Gross And Net Amounts Of Liabilities Presented In the Statement Of Financial Condition	4,282	4,197
Gross Amount of Liabilities Not Offset in the Statement of Financial Condition, Financial Instruments	3,025	3,983
Cash Collateral Pledged	1,257
Liability Net Amount		214
Reverse Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross and Net Amounts of Assets Presented in the Statement of Financial Condition	148,984	248,018
Gross Amounts Not Offset in the Statement of Financial Condition, Financial Instruments	148,394	248,018
Asset Net Amount	590
Repurchase Agreements
Offsetting Assets and Liabilities [Line Items]
Gross And Net Amounts Of Liabilities Presented In the Statement Of Financial Condition	316,352	142,266
Gross Amount of Liabilities Not Offset in the Statement of Financial Condition, Financial Instruments	$ 316,352	$ 142,266