Fair Value of Financial Instruments Financial Instruments Carried at Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	$ 46,444	$ 4,482
Financial liability carried at fair value	5,734	4,802
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member] | Interest rate swap agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liability carried at fair value	1,907	4,659
Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member] | Cross-currency swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial liability carried at fair value	3,827	143
Prepaid Expenses and Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member] | Cross-currency swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	17,117	255
Interest rate swap agreements [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	$ 29,327	$ 4,227