Derivatives Notional Amounts (Details) (USD $)	3 Months Ended																					12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2013 Foreign Exchange Forward [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / EUR [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / EUR [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / GBP [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / GBP [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] EUR / SEK [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] EUR / SEK [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / NZD [Member]	Mar. 31, 2012 Foreign Exchange Forward [Member] Not Designated as Hedging Instrument [Member] AUD / NZD [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] DKK / SEK [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] DKK / SEK [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / CAD [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / CAD [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / CHF [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / CHF [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / GBP [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / GBP [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / SEK [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / SEK [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / NZD [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] EUR / NZD [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / AUD [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / AUD [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / CHF [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / CHF [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / SEK [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] GBP / SEK [Member]	Mar. 31, 2013 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] NOK / CHF [Member]	Dec. 31, 2012 Foreign Exchange Forward [Member] Designated as Hedging Instrument [Member] NOK / CHF [Member]	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]
Derivative [Line Items]
Derivative, Percentage of Forcasted Transactions With Currency Rate Exposure																																																													60.00%	90.00%
Notional Amount of Derivatives, Matured During Period	$ 33,494,000	$ 36,967,000
Notional Amount			51,556,000	23,516,000	1,500,000	0	2,966,000	0	24,120,000	7,138,000	0	1,377,000	0	2,483,000	0	3,315,000	22,970,000	8,137,000	0	1,066,000	136,925,000	108,408,000	4,441,000	6,397,000	1,289,000	0	26,998,000	17,620,000	2,526,000	0	704,000	0	46,336,000	59,510,000	1,940,000	2,519,000	3,965,000	0	5,940,000	0	6,855,000	6,954,000	1,256,000	0	4,601,000	0	15,675,000	2,077,000	1,505,000	0	5,450,000	5,749,000	574,000	0	887,000	0	3,302,000	4,154,000	2,681,000	3,428,000
Unrealized Gain (Loss)																					841,000	(540,000)	95,000	(47,000)	(19,000)	0	(95,000)	(6,000)	(21,000)	0	25,000	0	(756,000)	(797,000)	102,000	(3,000)	32,000	0	144,000	0	430,000	141,000	0	0	79,000	0	156,000	46,000	(7,000)	0	311,000	105,000	(23,000)	0	(6,000)	0	291,000	25,000	103,000	(4,000)
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (1,171,000)	$ 83,000	$ (1,171,000)	$ 83,000	$ (35,000)	$ 0	$ 6,000	$ 0	$ (544,000)	$ 77,000	$ 0	$ 7,000	$ 0	$ (2,000)	$ 0	$ 63,000	$ (598,000)	$ (73,000)	$ 0	$ 11,000