Derivative Instruments - Offsetting of Derivative Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Gross Amount	$ 33,292	$ 33,317
Gross Amounts Offset in the Balance Sheet, Derivative Assets
Net Amount Presented in the Balance Sheet	33,292	33,317
Gross Amount	40,165	43,369
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities
Net Amount Presented in the Balance Sheet	40,165	43,369
Derivative Assets Subject to Master Netting Arrangement [Member]
Derivatives, Fair Value [Line Items]
Net Amount Presented in the Balance Sheet	2,213	3,579
Derivative Assets Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	2,172	3,547
Gross Amounts Offset in the Balance Sheet, Derivative Assets
Net Amount Presented in the Balance Sheet	2,172	3,547
Derivative Assets Subject to Master Netting Arrangement [Member] | Equity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	41	32
Gross Amounts Offset in the Balance Sheet, Derivative Assets
Net Amount Presented in the Balance Sheet	41	32
Derivative Assets Not Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	31,079	29,738
Gross Amounts Offset in the Balance Sheet, Derivative Assets
Net Amount Presented in the Balance Sheet	31,079	29,738
Derivative Liabilities Subject to Master Netting Arrangement [Member]
Derivatives, Fair Value [Line Items]
Net Amount Presented in the Balance Sheet	38,332	40,323
Derivative Liabilities Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	38,332	40,323
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities
Net Amount Presented in the Balance Sheet	38,332	40,323
Derivative Liabilities Not Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	1,792	3,014
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities
Net Amount Presented in the Balance Sheet	1,792	3,014
Derivative Liabilities Not Subject to Master Netting Arrangement [Member] | Equity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	41	32
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities
Net Amount Presented in the Balance Sheet	$ 41	$ 32