Summary of Derivative Financial Instruments Notional Amounts on Outstanding Positions (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Notional Amount of Derivatives [Abstract]
Latest maturity date	Dec. 01, 2015	Dec. 01, 2015
Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	$ 223,975	$ 143,116
Japanese Yen [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	73,584	112,500
Euro [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	48,063	5,159
Pound Sterling [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	24,653	8,742
Singapore Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	23,256
Mexican Peso [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	18,700	11,400
Russian Ruble [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	11,892
Australian Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	5,682	4,178
New Taiwan Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	4,353
South African Rand [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	3,250
South Korean Won [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	2,083
Swedish Krona [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	1,959
Canadian Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	1,698
Indian Rupee [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	1,600
Hong Kong Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	1,451
New Zealand Dollar [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	1,200	1,137
Norwegian Krone [Member] | Forward Contracts [Member]
Notional Amount of Derivatives [Abstract]
Notional value, net	$ 551