Derivative Financial Instruments - Summary of Fair Value of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Total derivative assets	$ 21,968	$ 18,572
Total derivative liabilities	31,259	23,868
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	5,325	4,278
Total derivative liabilities	15,935	9,951
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	5,325	4,278
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	15,935	9,951
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	16,643	14,294
Total derivative liabilities	15,324	13,917
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	15,032	13,780
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	15,169	13,917
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	1,611	514
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	$ 155