Derivative Financial Instruments Activity of Hedging Instruments in Accumulated OCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net unrealized loss on hedging instruments at January 1,	$ (16,069)	$ (14,380)
Unrealized gain (loss) on derivative instruments	(73)	0
Net unrealized loss on hedging instruments at March 31,	(16,142)	(14,380)
Net Investment Hedging [Member]
Net unrealized loss on hedging instruments at March 31,	$ (14,400)