Derivative Financial Instruments (Effect of Derivative Instruments on Earnings) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Loss Recognized In Income On Derivatives	$ 233	$ 128
Cash Flow Hedges [Member] | Interest Rate Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Gain Recognized In OCI	2,796	1,698
Interest Expense [Member] | Cash Flow Hedges [Member] | Interest Rate Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Loss Reclassified From Accumulated OCI Into Income	(4,534)	(4,280)
Other Expense [Member] | Interest Rate Contract [Member] | Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Loss Recognized In Income On Derivatives	(1)	(31)
Other Expense [Member] | Cash Flow Hedges [Member] | Interest Rate Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Loss Recognized In Income (Ineffective Portion)	0	0
Other Income [Member] | Interest Rate Contract [Member] | Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Loss Recognized In Income On Derivatives	$ (232)	$ (97)