Fair Values Of Assets And Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Funds, at Carrying Value	$ 1,105,275	$ 1,830,261
Interest Rate Cap Agreements Purchased	784	386
Investment Foreign Currency, Contract, Amount Purchased	2,221
Interest Rate Swap Agreements - Assets		133
Derivative Assets	1,108,280
Interest Rate Swap Agreements - Liabilities		133
Interest Rate Cap Agreements - Sold	795	394
Investment Foreign Currency, Contract, Amount Sold	2,257
Derivative Liabilities	3,052	527
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money Market Funds, at Carrying Value	1,105,275	1,830,261
Derivative Assets	1,105,275	1,830,261
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Cap Agreements Purchased	784	386
Investment Foreign Currency, Contract, Amount Purchased	2,221
Derivative Assets	3,005	386
Interest Rate Cap Agreements - Sold	795	394
Investment Foreign Currency, Contract, Amount Sold	2,257
Derivative Liabilities	3,052	394
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Swap Agreements - Assets		133
Derivative Assets		133
Interest Rate Swap Agreements - Liabilities		133
Derivative Liabilities		$ 133