Hedging Deferred net gains (losses) in AOCI expected to be reclassed into income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	$ (4,517)
Foreign currency derivatives [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	(8,279)
Bunker fuel forward contracts [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	6,576
2013 [Member] | Foreign currency derivatives [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	(12,390)
2013 [Member] | Bunker fuel forward contracts [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	4,807
2013 [Member] | Total [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	(7,583)
2014 [Member] | Foreign currency derivatives [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	4,111
2014 [Member] | Bunker fuel forward contracts [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	718
2014 [Member] | Total [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	4,829
2015 [Member] | Foreign currency derivatives [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	0
2015 [Member] | Bunker fuel forward contracts [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	1,051
2015 [Member] | Total [Member]
Derivative [Line Items]
Derivative instruments, gain (loss) reclassification from accumulated OCI to income, estimated net amount to be transferred	$ 1,051