Earnings Per Share ("EPS") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Feb. 28, 2019
Net Income (Loss) Attributable to Kraton, Basic:
As reported	$ 12,668	$ 22,072
Amounts allocated to unvested restricted shares	128	368
Amounts available to common stockholders	12,540	21,704
Net Income (Loss) Attributable to Kraton, Diluted:
Amounts allocated to unvested restricted shares	128	368
Amounts reallocated to unvested restricted shares	(127)	(361)
Amounts available to stockholders and assumed conversions	$ 12,541	$ 21,711
Weighted Average Shares Outstanding, Basic:
As reported (in shares)	31,956	31,771
Amounts allocated to unvested restricted shares (in shares)	(323)	(530)
Amounts available to common stockholders (in shares)	31,633	31,241
Weighted Average Shares Outstanding, Diluted:
Amounts allocated to unvested restricted shares (in shares)	(323)	(530)
Non participating share units (in shares)	205	280
Stock options added under the treasury stock method (in shares)	63	330
Amounts available to stockholders and assumed conversions (in shares)	31,901	31,851
Earnings (loss) per share, basic (in dollars per share)	$ 0.40	$ 0.69
Earnings (loss) per share, diluted (in dollars per share)	$ 0.39	$ 0.68
Stock repurchase program, authorized amount			$ 50,000