Hedging Exposure Future Cash Flows for Forecasted Transactions (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 10,700,000
Remaining Term in Months	31 months
Weighted Average Fixed Interest Rate in Contract	1.47%
12 Months Or Less
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	800,000
Remaining Term in Months	6 months
Weighted Average Fixed Interest Rate in Contract	2.05%
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	2,400,000
Remaining Term in Months	20 months
Weighted Average Fixed Interest Rate in Contract	1.76%
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	3,700,000
Remaining Term in Months	30 months
Weighted Average Fixed Interest Rate in Contract	1.73%
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	0.92%
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	$ 1,400,000
Remaining Term in Months	52 months
Weighted Average Fixed Interest Rate in Contract	0.89%
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