Derivative Financial Instruments - Summary of Fair Value of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Total derivative assets	$ 24,230	$ 36,512
Total derivative liabilities	22,373	30,010
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	3,974	6,458
Total derivative liabilities	2,188
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	3,974	6,458
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	2,188
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Total derivative assets	20,256	30,054
Total derivative liabilities	20,185	30,010
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	19,713	29,475
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	19,970	29,909
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member] | Other Assets [Member]
Derivative [Line Items]
Total derivative assets	543	579
Not Designated as Hedging Instrument [Member] | Mortgage Contracts [Member] | Other Liabilities [Member]
Derivative [Line Items]
Total derivative liabilities	$ 215	$ 101