401(k) Plan

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

401(k) Plan

14. 401(k) Plan

In 1992, we established a voluntary retirement plan under Section 401(k) of the Internal Revenue Code. The plan covers all employees with at least six months of employment with our company and provides the annual matching contributions by us at the discretion of our Board of Directors. Our expense for matching contributions to our voluntary retirement plan approximated $1.7 million, $1.6 million and $1.5 million in 2014, 2013 and 2012, respectively.