Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental disclosures:
Interest paid	$ 0us-gaap_InterestPaid	$ 1us-gaap_InterestPaid	$ 44us-gaap_InterestPaid
Income taxes paid, net	26,456us-gaap_IncomeTaxesPaidNet	19,884us-gaap_IncomeTaxesPaidNet	15,128us-gaap_IncomeTaxesPaidNet
Non-cash investing and financing activities:
Non-cash capital expenditures	(79)	71	(3,670)
Trade-in of equipment	$ 0	$ 315	$ 300

Future cash outflow to pay for purchases of fixed assets that have occurred.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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