Fair Value of Financial Instruments Financial Instruments Carried at Fair Value(Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets carried at fair value	$ 136	$ 53,043
Total financial liabilities carried at fair value	4,711	2,439
Designated as Hedging Instrument [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	136	36,987
Financial liabilities carried at fair value	4,711	2,439
Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	136	36,987
Financial liabilities carried at fair value	4,711	2,439
Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 2 [Member] | Cross-currency swap agreement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets carried at fair value	$ 0	$ 16,056