Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Supplemental non-cash investing and financing activities:
Value of common stock issued in acquisition of EOGA	$ 1,750	$ 0
Value of common stock issued in payment of accrued liability	600	0
Equipment acquired through capital leases	0	480
Exercise of stock options by common stock surrender	1,005	2,357
Supplemental cash payment information:
Interest paid	360	381
Income taxes paid	$ 2,039	$ 3,537