Derivative Financial Instruments (Effect of Derivative Instruments on Earnings) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Gain (Loss) Recognized In Income On Derivatives	$ 1,848	$ (124)	$ 1,615	$ (138)
Cash Flow Hedges [Member] | Interest Rate Contract [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Gain (Loss) Recognized In OCI	6,401	(4,178)	9,199	(2,480)
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	(4,668)	(4,369)	(9,202)	(8,649)
Other Expense [Member] | Interest Rate Contract [Member] | Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Gain (Loss) Recognized In Income On Derivatives	0	(6)	(1)	(37)
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	0	0
Other Income [Member] | Interest Rate Contract [Member] | Not Designated As Hedging Instruments [Member]
Derivative Instruments Gain Loss [Line Items]
Amount Of Gain (Loss) Recognized In Income On Derivatives	$ 1,848	$ (118)	$ 1,616	$ (101)