Derivative Financial Instruments (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		3 Months Ended		6 Months Ended					6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Jun. 30, 2012 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Jun. 30, 2013 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Jun. 30, 2012 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Jun. 30, 2013 Cash Flow Hedges [Member]	Dec. 31, 2012 Cash Flow Hedges [Member]	Jun. 30, 2012 Cash Flow Hedges [Member]	Jun. 30, 2013 Cash Flow Hedges [Member] Interest Expense [Member]	Dec. 31, 2012 Cash Flow Hedges [Member] Interest Rate Swaps [Member] DerivativeInstruments	Jun. 30, 2012 Cash Flow Hedges [Member] Interest Rate Swaps [Member] DerivativeInstruments
Derivative [Line Items]
Aggregate notional amount designated as cash flow hedges							$ 1,150,284	$ 1,154,363	$ 1,158,615
Number of derivative instruments held			263	93	263	93					14	14
Future annual time period	12 months
Estimated amount to be reclassified										20,382
Aggregate notional amount derivative			1,605,531	674,814	1,605,531	674,814
Net gain (loss) related to changes in fair value of derivatives			1,848	(124)	1,615	(138)
Fair value of derivatives in net liability position with credit-risk-related Contingent Features	58,146	72,126
Cash collateral posted with derivative counterparties	$ 45,241	$ 75,103