Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Supplemental non-cash investing and financing activities:
Value of common stock issued in acquisitions	$ 1,014	$ 1,900
Value of common stock issued in payment of accrued liability	0	600
Exercise of stock options by common stock surrender	1,126	1,005
Supplemental cash payment information:
Interest paid	641	710
Income taxes paid	$ 2,549	$ 13,884