Derivative Instruments and Hedging Activities (Details) (Foreign Exchange [Member], USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	$ 1,882,240	$ 1,632,281
Australian Dollar [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	40,085	51,809
British Pound [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	29,987	58,440
Canadian Dollar [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	160,897	133,128
Euro [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	1,018,285	675,438
Japanese Yen [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	558,717	632,962
Swiss Franc [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	74,269	77,669
Others [Member]
Foreign currency forward contracts entered into hedge
Notional amount of net investment hedging instruments, Total	$ 0	$ 2,835