Derivative and Hedging Activities - Offsetting of Derivative Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross Amount	$ 54,431	$ 46,160
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities	0	0
Net Amount Presented in the Balance Sheet	54,431us-gaap_DerivativeLiabilities	46,160us-gaap_DerivativeLiabilities
Subject to Master Netting Arrangement [Member]
Derivatives, Fair Value [Line Items]
Net Amount Presented in the Balance Sheet	54,387	45,985
Subject to Master Netting Arrangement [Member] \| Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	669	2,330
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities	0	0
Net Amount Presented in the Balance Sheet	669	2,330
Subject to Master Netting Arrangement [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	53,718	43,655
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities	0	0
Net Amount Presented in the Balance Sheet	53,718	43,655
Not Subject to Master Netting Arrangement [Member]
Derivatives, Fair Value [Line Items]
Net Amount Presented in the Balance Sheet	44	175
Not Subject to Master Netting Arrangement [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	5	128
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities	0	0
Net Amount Presented in the Balance Sheet	5	128
Not Subject to Master Netting Arrangement [Member] \| Equity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amount	39	47
Gross Amounts Offset in the Balance Sheet, Derivative Liabilities	0	0
Net Amount Presented in the Balance Sheet	$ 39	$ 47

Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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