Hedging Exposure Future Cash Flows for Forecasted Transactions (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 10,900,000
Remaining Term in Months	34 months
Weighted Average Fixed Interest Rate in Contract	1.48%
12 Months Or Less
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	900,000
Remaining Term in Months	7 months
Weighted Average Fixed Interest Rate in Contract	2.00%
12 Months Or Less | Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	0 months
12 Months Or Less | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	12 months
Over 12 Months To 24 Months
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,600,000
Remaining Term in Months	20 months
Weighted Average Fixed Interest Rate in Contract	1.92%
Over 12 Months To 24 Months | Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	12 months
Over 12 Months To 24 Months | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	24 months
Over 24 Months To 36 Months
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	4,000,000
Remaining Term in Months	31 months
Weighted Average Fixed Interest Rate in Contract	1.70%
Over 24 Months To 36 Months | Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	24 months
Over 24 Months To 36 Months | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	36 months
Over 36 Months To 48 Months
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	2,400,000
Remaining Term in Months	42 months
Weighted Average Fixed Interest Rate in Contract	1.10%
Over 36 Months To 48 Months | Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	36 months
Over 36 Months To 48 Months | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	48 months
Over 48 Months To 60 Months
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 2,000,000
Remaining Term in Months	53 months
Weighted Average Fixed Interest Rate in Contract	0.88%
Over 48 Months To 60 Months | Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	48 months
Over 48 Months To 60 Months | Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Maturity - remaining maturity range	60 months