Derivative Financial Instruments (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		3 Months Ended				3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Mar. 31, 2012 Not Designated As Hedging Instruments [Member] DerivativeInstruments	Mar. 31, 2013 Cash Flow Hedges [Member]	Mar. 31, 2012 Cash Flow Hedges [Member]	Mar. 31, 2013 Cash Flow Hedges [Member] Interest Expense [Member]	Mar. 31, 2013 Cash Flow Hedges [Member] Interest Rate Swaps [Member] DerivativeInstruments	Mar. 31, 2012 Cash Flow Hedges [Member] Interest Rate Swaps [Member] DerivativeInstruments
Derivative [Line Items]
Aggregate notional amount designated as cash flow hedges					$ 1,152,298	$ 1,160,778
Number of derivative instruments held			231	95				14	14
Future annual time period	12 months
Estimated amount to be reclassified							19,784
Aggregate notional amount derivative			1,392,430	682,447
Net loss related to changes in fair value of derivatives			233	128
Fair value of derivatives in net liability position with credit-risk-related Contingent Features	67,111	72,126
Cash collateral posted with derivative counterparties	$ 67,920	$ 75,103