Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 2,332	$ 2,531
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Common stock, par value	$ 0.2	$ 0.2
Common stock, shares authorized	175,000,000	175,000,000
Common stock, shares issued	55,443,393	54,055,600
Other Comprehensive Income (Loss), Tax	$ 0	$ (155)
VIE Current assets pledged	28,800	40,100
VIE Non-current assets pledged	434,300	423,300
VIE Current liabilities, no recourse	32,200	42,800
VIE Non-current liabilities, no recourse	$ 26,000	$ 14,700