Accounting Policies - Financial Data for Variable Interest Entities - Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Current assets	$ 52,709	$ 57,046
Non-current assets	41,125	43,165
Current liabilities	19,563	22,525
Non-current liabilities	$ 35,236	$ 36,155