Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental non-cash investing and financing activities:
Value of common stock issued in payment of accrued liability	$ 0	$ 188
Exercise of stock options by common stock surrender	0	5,863
Supplemental cash payment information:
Interest paid	1,645	1,511
Income taxes paid, net of refunds (received, net of payments)	$ 16	$ (10,081)