Industry Segments - Revenue by type of service (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 category	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customer [Line Items]
Number of Revenue Categories by Type of Service									2
Revenue	$ 52,351	$ 41,299	$ 47,334	$ 57,053	$ 59,569	$ 44,410	$ 47,544	$ 51,351	$ 198,037	$ 202,874	$ 240,458
Acquisition and Licensing of Seismic Data [Member]
Revenue from External Customer [Line Items]
Revenue									194,037	198,109	234,785
Reproduction and Delivery of Seismic Data and Other Services [Member]
Revenue from External Customer [Line Items]
Revenue									$ 4,000	$ 4,765	$ 5,673