Derivative Financial Instruments (Schedule of Interest Rate Swap Agreements) (Details) In Thousands, unless otherwise specified	Mar. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2013 South African Facility [Member] ZAR		Dec. 31, 2012 South African Facility [Member] ZAR		Mar. 31, 2013 Colombian Long Term Credit Facility [Member] COP		Dec. 31, 2012 Colombian Long Term Credit Facility [Member] COP
Derivative [Line Items]
Derivative, Notional Amount	$ 101,128	$ 107,256	423,634	[1]	423,634	[2]	101,250,000	[1]	101,250,000	[2]
Carrying Amount and Fair Value	$ 5,645	$ 5,442	14,841	[1]	20,441	[2]	7,398,809	[1]	5,356,377	[2]

[1] The interest rate swap agreements are denominated in ZAR and COP and have an aggregate notional amount and fair value of $101.1 million and $5.6 million, respectively, as of March 31, 2013.

[2] The interest rate swap agreements are denominated in ZAR and COP and have an aggregate notional amount and fair value of $107.3 million and $5.4 million, respectively, as of December 31, 2012.