Derivatives - Interest Rate Swap Agreements (Hedging Exposure Future Cash Flows For Forecasted Transactions) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Derivative [Line Items]
Maturity - average period of months	34
Notional Amount	$ 7,300,000
Weighted Average Fixed Interest Rate in Contract	1.78%
12 Months Or Less [Member]
Derivative [Line Items]
Maturity - lower remaining maturity range	12 months or less
Maturity - higher remaining maturity range	0 months
Notional Amount	400,000
Remaining Term in Months	10
Weighted Average Fixed Interest Rate in Contract	1.75%
Over 12 Months To 24 Months [Member]
Derivative [Line Items]
Maturity - lower remaining maturity range	12 months
Maturity - higher remaining maturity range	Over 24 months
Notional Amount	800,000
Remaining Term in Months	18
Weighted Average Fixed Interest Rate in Contract	2.05%
Over 24 Months To 36 Months [Member]
Derivative [Line Items]
Maturity - lower remaining maturity range	24 months
Maturity - higher remaining maturity range	Over 36 months
Notional Amount	2,400,000
Remaining Term in Months	32
Weighted Average Fixed Interest Rate in Contract	1.76%
Over 36 Months To 48 Months [Member]
Derivative [Line Items]
Maturity - lower remaining maturity range	36 months
Maturity - higher remaining maturity range	Over 48 months
Notional Amount	$ 3,700,000
Remaining Term in Months	42
Weighted Average Fixed Interest Rate in Contract	1.73%