Borrowings (Details 2) - USD ($) $ in Thousands	Jan. 31, 2014	Jun. 30, 2015	Dec. 31, 2014
Credit Agreement
Term loan			$ 2,653
Obligations under capital leases		$ 11,962	15,128
Total		11,962	$ 17,781
New Credit Agreement
Credit Agreement
Current borrowing capacity	$ 150,000
Credit facility initial term	2 years
Maximum borrowing capacity including accordion expansion	$ 225,000
Amount outstanding under Credit Agreement		$ 0