Trinseo (TSE) 10-Q 30 Jul 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 27, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-36473
Entity Registrant Name	Trinseo S.A.
Entity Incorporation, State or Country Code	N4
Entity Tax Identification Number	00-0000000
Entity Address, Address Line One	1000 Chesterbrook Boulevard
Entity Address, Address Line Two	Suite 300
Entity Address, Address Line Three	Berwyn
Entity Address, City or Town	Berwyn, PA 19312
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19312
City Area Code	610
Local Phone Number	240-3200
Title of 12(b) Security	Ordinary Shares, par value $0.01 per share
Trading Symbol	TSE
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		38,268,724
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001519061
Current Fiscal Year End Date	--12-31
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 581.8	$ 456.2
Accounts receivable, net of allowance for doubtful accounts (June 30, 2020: $5.7; December 31, 2019: $5.3)	432.2	570.8
Inventories	313.3	438.2
Other current assets	12.2	25.9
Total current assets	1,339.5	1,491.1
Investments in unconsolidated affiliates	212.3	188.1
Property, plant and equipment, net of accumulated depreciation (June 30, 2020: $738.6; December 31, 2019: $665.7)	573.5	625.8
Other assets
Goodwill	67.7	67.7
Other intangible assets, net	184.4	191.5
Right of use assets - operating	75.3	71.4
Deferred income tax assets	82.5	67.5
Deferred charges and other assets	54	55.7
Total other assets	463.9	453.8
Total assets	2,589.2	2,758.8
Current liabilities
Short-term borrowings and current portion of long-term debt	11.7	11.1
Accounts payable	213.6	343
Current lease liabilities - operating	15.2	14.1
Income taxes payable	59	5
Accrued expenses and other current liabilities	136.1	154.4
Total current liabilities	435.6	527.6
Noncurrent liabilities
Long-term debt, net of unamortized deferred financing fees	1,261.3	1,162.6
Noncurrent lease liabilities - operating	63.2	58
Deferred income tax liabilities	47.9	41.5
Other noncurrent obligations	322.4	300.2
Total noncurrent liabilities	1,694.8	1,562.3
Commitments and contingencies (Note 15)
Shareholders' equity
Ordinary shares, $0.01 nominal value, 50,000.0 shares authorized (June 30, 2020: 48.8 shares issued and 38.3 shares outstanding; December 31, 2019: 48.8 shares issued and 39.0 shares outstanding)	0.5	0.5
Additional paid-in-capital	576.3	574.7
Treasury shares, at cost (June 30, 2020: 10.5 shares; December 31, 2019: 9.8 shares)	(547.3)	(524.9)
Retained earnings	585.4	781
Accumulated other comprehensive loss	(156.1)	(162.4)
Total shareholders' equity	458.8	668.9
Total liabilities and shareholders' equity	$ 2,589.2	$ 2,758.8

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Condensed Consolidated Balance Sheets
Allowance for doubtful accounts	$ 5.7	$ 5.3
Accumulated depreciation	$ 738.6	$ 665.7
Ordinary shares, nominal value	$ 0.01	$ 0.01
Ordinary shares, shares authorized	50,000,000,000	50,000,000,000
Ordinary shares, shares issued	48,800,000	48,800,000
Ordinary shares, shares outstanding	38,300,000	39,000,000
Treasury stock, shares	10,500,000	9,800,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statements of Operations
Net sales	$ 569.7	$ 951.8	$ 1,423.2	$ 1,964.9
Cost of sales	576.8	865.6	1,360.6	1,781.2
Gross profit (loss)	(7.1)	86.2	62.6	183.7
Selling, general and administrative expenses	58.3	71.4	135.8	140.3
Equity in earnings of unconsolidated affiliates	14.4	40.3	24.2	72.5
Impairment charges			38.3
Operating income (loss)	(51)	55.1	(87.3)	115.9
Interest expense, net	11.7	9.9	22	20.1
Other expense, net	1	1.5	2.6	5.5
Income (loss) before income taxes	(63.7)	43.7	(111.9)	90.3
Provision for (benefit from) income taxes	64.7	15.7	52.8	26.5
Net income (loss)	$ (128.4)	$ 28	$ (164.7)	$ 63.8
Weighted average shares- basic	38.2	40.8	38.4	41
Net income (loss) per share- basic	$ (3.36)	$ 0.69	$ (4.29)	$ 1.56
Weighted average shares- diluted	38.2	41.1	38.4	41.5
Net income (loss) per share- diluted	$ (3.36)	$ 0.68	$ (4.29)	$ 1.54

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ (128.4)	$ 28	$ (164.7)	$ 63.8
Other comprehensive income (loss), net of tax
Cumulative translation adjustments	(1.1)	3	9.6	2.7
Net loss on cash flow hedges	(1.3)	(5.4)	(5)	(5.3)
Pension and other postretirement benefit plans:
Net gain (loss) during period (net of tax of: $0.0, $0.0, $0.1 and $(0.2))			0.6	(2)
Amounts reclassified from accumulated other comprehensive income	0.5	0.3	1.1	1.3
Total other comprehensive income (loss), net of tax	(1.9)	(2.1)	6.3	(3.3)
Comprehensive income (loss)	$ (130.3)	$ 25.9	$ (158.4)	$ 60.5

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statements of Comprehensive Income (Loss)
Net gain (loss) during period, tax (benefit) expense	$ 0	$ 0	$ 0.1	$ (0.2)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Ordinary Shares	Additional Paid-In Capital	Treasury Shares	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
Balance at beginning of period at Dec. 31, 2018	$ 0.5	$ 575.4	$ (418.1)	$ (142.3)	$ 753.2	$ 768.7
Balance at beginning of period, shares at Dec. 31, 2018	41.6		7.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					35.8	35.8
Other comprehensive income (loss)				(1.2)		(1.2)
Stock-based compensation		(6.6)	$ 7			0.4
Stock-based compensation, shares	0.1		(0.1)
Purchase of treasury shares			$ (34)			(34)
Purchase of treasury shares, shares	(0.7)		0.7
Dividends on ordinary shares					(16.6)	(16.6)
Balance at end of period at Mar. 31, 2019	$ 0.5	568.8	$ (445.1)	(143.5)	772.4	753.1
Balance at end of period, shares at Mar. 31, 2019	41		7.8
Balance at beginning of period at Dec. 31, 2018	$ 0.5	575.4	$ (418.1)	(142.3)	753.2	768.7
Balance at beginning of period, shares at Dec. 31, 2018	41.6		7.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)						63.8
Other comprehensive income (loss)						(3.3)
Balance at end of period at Jun. 30, 2019	$ 0.5	571.2	$ (465.1)	(145.6)	784.1	745.1
Balance at end of period, shares at Jun. 30, 2019	40.6		8.2
Balance at beginning of period at Mar. 31, 2019	$ 0.5	568.8	$ (445.1)	(143.5)	772.4	753.1
Balance at beginning of period, shares at Mar. 31, 2019	41		7.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					28	28
Other comprehensive income (loss)				(2.1)		(2.1)
Stock-based compensation		2.4	$ 1.7			4.1
Stock-based compensation, shares	0.1		(0.1)
Purchase of treasury shares			$ (21.7)			(21.7)
Purchase of treasury shares, shares	(0.5)		0.5
Dividends on ordinary shares					(16.3)	(16.3)
Balance at end of period at Jun. 30, 2019	$ 0.5	571.2	$ (465.1)	(145.6)	784.1	745.1
Balance at end of period, shares at Jun. 30, 2019	40.6		8.2
Balance at beginning of period at Dec. 31, 2019	$ 0.5	574.7	$ (524.9)	(162.4)	781	$ 668.9
Balance at beginning of period, shares at Dec. 31, 2019	39		9.8			39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					(36.3)	$ (36.3)
Other comprehensive income (loss)				8.2		8.2
Stock-based compensation		1	$ 1.7			2.7
Purchase of treasury shares			$ (25)			(25)
Purchase of treasury shares, shares	(0.8)		0.8
Dividends on ordinary shares					(15.5)	(15.5)
Balance at end of period at Mar. 31, 2020	$ 0.5	575.7	$ (548.2)	(154.2)	729.2	603
Balance at end of period, shares at Mar. 31, 2020	38.2		10.6
Balance at beginning of period at Dec. 31, 2019	$ 0.5	574.7	$ (524.9)	(162.4)	781	$ 668.9
Balance at beginning of period, shares at Dec. 31, 2019	39		9.8			39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)						$ (164.7)
Other comprehensive income (loss)						6.3
Balance at end of period at Jun. 30, 2020	$ 0.5	576.3	$ (547.3)	(156.1)	585.4	$ 458.8
Balance at end of period, shares at Jun. 30, 2020	38.3		10.5			38.3
Balance at beginning of period at Mar. 31, 2020	$ 0.5	575.7	$ (548.2)	(154.2)	729.2	$ 603
Balance at beginning of period, shares at Mar. 31, 2020	38.2		10.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					(128.4)	(128.4)
Other comprehensive income (loss)				(1.9)		(1.9)
Stock-based compensation		0.6	$ 0.9			1.5
Stock-based compensation, shares	0.1		(0.1)
Dividends on ordinary shares					(15.4)	(15.4)
Balance at end of period at Jun. 30, 2020	$ 0.5	$ 576.3	$ (547.3)	$ (156.1)	$ 585.4	$ 458.8
Balance at end of period, shares at Jun. 30, 2020	38.3		10.5			38.3

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Shareholders' Equity (Parenthetical)) - $ / shares	3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
Condensed Consolidated Statement of Stockholders' Equity
Dividends on ordinary shares	$ 0.40	$ 0.40	$ 0.40	$ 0.40

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net income (loss)	$ (164.7)	$ 63.8
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Depreciation and amortization	71.1	68.7
Amortization of deferred financing fees, issuance discount, and excluded component of hedging instruments	1.6	(0.2)
Deferred income tax	(12)	0.3
Share-based compensation expense	6.3	7.7
Earnings of unconsolidated affiliates, net of dividends	(24.2)	(20)
Unrealized net (gain) loss on foreign exchange forward contracts	(2)	5.5
Gain on sale of businesses and other assets	(0.4)	(0.2)
Impairment charges	38.3
Pension settlement loss		0.7
Changes in assets and liabilities
Accounts receivable	129.9	24.1
Inventories	123.1	50.7
Accounts payable and other current liabilities	(137)	45.1
Income taxes payable	54	(11.2)
Other assets, net	(15.1)	1
Other liabilities, net	6.9	(2)
Cash provided by operating activities	75.8	234
Cash flows from investing activities
Capital expenditures	(48.2)	(47.6)
Net cash received for asset and business acquisitions, net of cash acquired	0.1
Proceeds from the sale of businesses and other assets	11.9	0.7
Proceeds from the settlement of hedging instruments	51.6
Cash provided by (used in) investing activities	15.4	(46.9)
Cash flows from financing activities
Short-term borrowings, net	(5.4)	(2.3)
Purchase of treasury shares	(25)	(59.1)
Dividends paid	(31.2)	(33.8)
Proceeds from exercise of option awards		0.8
Withholding taxes paid on restricted share units	(0.6)	(4)
Repayments of 2024 Term Loan B	(3.4)	(3.5)
Net proceeds from draw on 2022 Revolving Facility	100
Cash provided by (used in) financing activities	34.4	(101.9)
Effect of exchange rates on cash	(0.5)	(1.6)
Net change in cash, cash equivalents and restricted cash	125.1	83.6
Cash, cash equivalents and restricted cash, beginning of period	457.4	452.3
Cash, cash equivalents and restricted cash, end of period	582.5	535.9
Restricted cash	$ (0.7)	$ (1)
Restricted Cash and Cash Equivalents, Current, Asset, Statement of Financial Position [Extensible List]	Other Assets, Current	Other Assets, Current
Cash and cash equivalents, end of period	$ 581.8	$ 534.9

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2020
Basis of Presentation
Basis of Presentation	NOTE 1—BASIS OF PRESENTATION The unaudited interim condensed consolidated financial statements of Trinseo S.A. and its subsidiaries (the “Company”) as of and for the periods ended June 30, 2020 and 2019 were prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and reflect all adjustments, consisting only of normal recurring adjustments, which, in the opinion of management, are considered necessary for the fair statement of the results for the periods presented. Because they cover interim periods, the statements and related notes to the financial statements do not include all disclosures normally provided in annual financial statements, and therefore, these statements should be read in conjunction with the 2019 audited consolidated financial statements included within the Company’s Annual Report on Form 10-K (“Annual Report”) filed with the Securities and Exchange Commission (“SEC”) on February 28, 2020. The effects of the COVID-19 pandemic have negatively impacted the Company’s results of operations, cash flows and financial position in 2020. The Company expects these negative effects to continue, which future impacts could be material, and dependent on numerous factors that are highly uncertain, for which the ultimate impact cannot be predicted at this time, including the duration and scope of the COVID-19 pandemic. The Company’s condensed consolidated financial statements presented herein reflect the latest estimates and assumptions made by management that affect the reported amounts and related disclosures as of and for the period ended June 30, 2020. However, actual results could differ from these estimates and assumptions. The December 31, 2019 condensed consolidated balance sheet data presented herein was derived from the Company’s December 31, 2019 audited consolidated financial statements, but does not include all disclosures required by GAAP for annual periods. ​

Recent Accounting Guidance

Recent Accounting Guidance	6 Months Ended
	Jun. 30, 2020
Recent Accounting Guidance
Recent Accounting Guidance	NOTE 2—RECENT ACCOUNTING GUIDANCE In August 2018, the Financial Accounting Standards Board (“FASB”) issued guidance which aligns the requirements for capitalizing implementation costs incurred in a cloud computing hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The Company adopted this standard prospectively, effective January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. In December 2019, the FASB issued guidance that simplifies the accounting for income taxes. The amended guidance includes removal of certain exceptions to the general principles of Accounting Standards Codification 740, Income Taxes, and simplification in several other areas such as accounting for a franchise tax (or similar tax) that is partially based on income. This guidance is effective for public business entities for interim and annual reporting periods beginning after December 15, 2020, with early adoption permitted. The Company is currently assessing the timing and impacts of adopting this guidance on its consolidated financial statements. In March 2020, the FASB issued optional guidance for a limited period of time to ease the potential burden in accounting for the effects of the transition away from London Interbank Offered Rate (“LIBOR”) and other reference rates. The Company adopted this guidance upon issuance, noting that it did not have a material impact on the Company’s condensed consolidated financial statements.

Net Sales

Net Sales	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Net Sales	NOTE 3—NET SALES Refer to the Annual Report for information on the Company's accounting policies and further background related to its net sales. The following table provides disclosure of net sales to external customers by primary geographical market (based on the location where sales originated), by segment for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Total June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 50.9 ​ $ — ​ $ 37.4 ​ $ — ​ $ 1.3 ​ $ 89.6 ​ Europe ​ 72.3 ​ 34.9 ​ 97.8 ​ 95.1 ​ 20.6 ​ 320.7 ​ Asia-Pacific ​ 40.4 ​ 1.5 ​ 48.1 ​ 60.7 ​ 1.7 ​ ​ 152.4 ​ Rest of World ​ 1.3 ​ ​ — ​ 5.7 ​ — ​ — ​ 7.0 ​ Total ​ $ 164.9 ​ $ 36.4 ​ $ 189.0 ​ $ 155.8 ​ $ 23.6 ​ $ 569.7 ​ June 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 67.2 ​ $ — ​ $ 78.4 ​ $ — ​ $ 2.4 ​ $ 148.0 ​ Europe ​ 99.2 ​ 112.1 ​ 187.3 ​ 115.9 ​ 33.2 ​ 547.7 ​ Asia-Pacific ​ 60.8 ​ — ​ 59.7 ​ 91.2 ​ 19.3 ​ ​ 231.0 ​ Rest of World ​ 3.0 ​ ​ — ​ 22.1 ​ — ​ — ​ 25.1 ​ Total ​ $ 230.2 ​ $ 112.1 ​ $ 347.5 ​ $ 207.1 ​ $ 54.9 ​ $ 951.8 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Total June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 113.1 ​ $ — ​ $ 108.0 ​ $ — ​ $ 3.9 ​ $ 225.0 ​ Europe ​ 174.2 ​ 134.6 ​ 262.8 ​ 204.9 ​ 49.7 ​ 826.2 ​ Asia-Pacific ​ 92.8 ​ 3.4 ​ 97.9 ​ 133.7 ​ 14.8 ​ 342.6 ​ Rest of World ​ 3.9 ​ ​ — ​ 25.5 ​ — ​ — ​ 29.4 ​ Total ​ $ 384.0 ​ $ 138.0 ​ $ 494.2 ​ $ 338.6 ​ $ 68.4 ​ $ 1,423.2 ​ June 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 130.5 ​ $ — ​ $ 160.2 ​ $ — ​ $ 5.1 ​ $ 295.8 ​ Europe ​ 200.6 ​ 236.7 ​ 400.7 ​ 254.1 ​ 73.6 ​ 1,165.7 ​ Asia-Pacific ​ 117.3 ​ — ​ 111.2 ​ 181.5 ​ 43.0 ​ ​ 453.0 ​ Rest of World ​ 5.7 ​ ​ — ​ 44.7 ​ — ​ — ​ 50.4 ​ Total ​ $ 454.1 ​ $ 236.7 ​ $ 716.8 ​ $ 435.6 ​ $ 121.7 ​ $ 1,964.9 ​ ​

Investments in Unconsolidated A

Investments in Unconsolidated Affiliates	6 Months Ended
	Jun. 30, 2020
Investments in Unconsolidated Affiliates
Investments in Unconsolidated Affiliates	NOTE 4—INVESTMENTS IN UNCONSOLIDATED AFFILIATES The Company’s investments held in unconsolidated affiliates are accounted for by the equity method. The Company is currently supplemented by one joint venture, Americas Styrenics LLC (“Americas Styrenics,” a styrene and polystyrene joint venture with Chevron Phillips Chemical Company LP). The results of Americas Styrenics are included within its own reporting segment. Americas Styrenics is a privately held company; therefore, a quoted market price for its equity interests is not available. The summarized financial information of the Company’s unconsolidated affiliate is shown below. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Sales $ 225.4 $ 418.4 $ 547.5 $ 787.6 ​ Gross profit ​ $ 31.3 ​ $ 85.9 ​ $ 38.4 ​ $ 140.1 ​ Net income ​ $ 20.1 ​ $ 72.8 ​ $ 11.8 ​ $ 115.7 ​ ​ Americas Styrenics As of June 30, 2020 and December 31, 2019, the Company’s investment in Americas Styrenics was $212.3 million and $188.1 million, respectively, which was $7.8 million and $(10.3) million greater (less) than the Company’s 50% share of the underlying net assets of Americas Styrenics, respectively. This amount represents the difference between the book value of assets contributed to the joint venture at the time of formation (May 1, 2008) and the Company’s 50% share of the total recorded value of the joint venture’s assets and certain adjustments to conform with the Company’s accounting policies. This difference is being amortized over the weighted average remaining useful life of the contributed assets of approximately 1.9 years as of June 30, 2020. The Company did not receive dividends from Americas Styrenics during the three and six months ended June 30, 2020 and received dividends of $40.0 million and $52.5 million from Americas Styrenics during the three and six months ended June 30, 2019, respectively.

Inventories

Inventories	6 Months Ended
	Jun. 30, 2020
Inventories
Inventories	NOTE 5—INVENTORIES Inventories consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Finished goods $ 148.5 $ 210.8 Raw materials and semi-finished goods ​ 127.0 ​ 190.1 Supplies ​ 37.8 ​ 37.3 Total ​ $ 313.3 ​ $ 438.2 ​

Debt

Debt	6 Months Ended
	Jun. 30, 2020
Debt
Debt	NOTE 6—DEBT Refer to the Annual Report for definitions of capitalized terms not included herein and further background on the Company’s debt structure discussed below. The Company was in compliance with all debt related covenants as of June 30, 2020 and December 31, 2019. As of June 30, 2020 and December 31, 2019, debt consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ December 31, 2019 ​ ​ Interest Rate as of Maturity Date Carrying Amount Unamortized Deferred Financing Fees (1) Total Debt, Less Unamortized Deferred Financing Fees Carrying Amount Unamortized Deferred Financing Fees (1) Total Debt, Less ​ Senior Credit Facility ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2024 Term Loan B ​ 2.178% ​ September 2024 ​ $ 680.8 ​ $ (12.3) ​ $ 668.5 ​ $ 684.3 ​ $ (13.7) ​ $ 670.6 ​ 2022 Revolving Facility (2) ​ Various ​ September 2022 ​ ​ 100.0 ​ ​ — ​ ​ 100.0 ​ ​ — ​ ​ — ​ ​ — ​ 2025 Senior Notes ​ 5.375% ​ September 2025 ​ ​ 500.0 ​ ​ (6.7) ​ ​ 493.3 ​ ​ 500.0 ​ ​ (7.3) ​ ​ 492.7 ​ Accounts Receivable Securitization Facility (3) ​ Various ​ September 2021 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Other indebtedness ​ Various ​ Various ​ ​ 11.2 ​ ​ — ​ ​ 11.2 ​ ​ 10.4 ​ ​ — ​ ​ 10.4 ​ Total debt ​ ​ ​ ​ ​ $ 1,292.0 ​ $ (19.0) ​ $ 1,273.0 ​ $ 1,194.7 ​ $ (21.0) ​ $ 1,173.7 ​ Less: current portion (4) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (11.7) ​ ​ ​ ​ ​ ​ ​ ​ (11.1) ​ Total long-term debt, net of unamortized deferred financing fees ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,261.3 ​ ​ ​ ​ ​ ​ ​ $ 1,162.6 ​ (1) This caption does not include deferred financing fees related to the Company’s revolving facilities, which are included within “Deferred charges and other assets” on the condensed consolidated balance sheets. (2) As of June 30, 2020, under the 2022 Revolving Facility, the Company had a capacity of $375.0 million, with $100.0 million of outstanding borrowings, resulting in incremental funds available for borrowing of $261.0 million (net amount available due to $14.0 million outstanding letters of credit). Additionally, the Company is required to pay a quarterly commitment fee in respect of any unused commitments under this facility equal to 0.375% per annum. On July 24, 2020, the Company repaid the $100.0 million of outstanding borrowings on the 2022 Revolving Facility. (3) As of June 30, 2020, this facility had a borrowing capacity of $150.0 million, and the Company had approximately $110.3 million of accounts receivable available to support this facility, based on the pool of eligible accounts receivable. In regard to outstanding borrowings, fixed interest charges are 1.95% plus variable commercial paper rates, while for available, but undrawn commitments, fixed interest charges are 1.00%. (4) As of June 30, 2020 and December 31, 2019, the current portion of long-term debt primarily related to $7.0 million of the scheduled future principal payments on the 2024 Term Loan B.

Goodwill

Goodwill	6 Months Ended
	Jun. 30, 2020
Goodwill.
Goodwill	NOTE 7—GOODWILL The following table shows changes in the carrying amount of goodwill, by segment, from December 31, 2019 to June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas ​ ​ ​ ​ Binders Rubber Plastics Polystyrene Feedstocks Styrenics Total Balance at December 31, 2019 ​ $ 15.6 ​ $ 11.0 ​ $ 36.7 ​ $ 4.4 ​ $ — ​ $ — ​ $ 67.7 ​ Foreign currency impact * ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ — ​ Balance at June 30, 2020 ​ $ 15.6 ​ $ 11.0 ​ $ 36.7 ​ $ 4.4 ​ $ — ​ $ — ​ $ 67.7 ​ * For the six months ended June 30, 2020, foreign currency impact on goodwill balances totaled less than $0.1 million. .

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2020
Derivative Instruments [Abstract]
Derivative Instruments	NOTE 8—DERIVATIVE INSTRUMENTS The Company’s ongoing business operations expose it to various risks, including fluctuating foreign exchange rates and interest rate risk. To manage these risks, the Company periodically enters into derivative financial instruments, such as foreign exchange forward contracts and interest rate swap agreements. The Company does not hold or enter into financial instruments for trading or speculative purposes. All derivatives are recorded on the condensed consolidated balance sheets at fair value. Foreign Exchange Forward Contracts Certain subsidiaries have assets and liabilities denominated in currencies other than their respective functional currencies, which creates foreign exchange risk. The Company’s principal strategy in managing its exposure to changes in foreign currency exchange rates is to naturally hedge the foreign currency-denominated liabilities on its balance sheet against corresponding assets of the same currency, such that any changes in liabilities due to fluctuations in exchange rates are offset by changes in their corresponding foreign currency assets. In order to further reduce this exposure, the Company also uses foreign exchange forward contracts to economically hedge the impact of the variability in exchange rates on assets and liabilities denominated in certain foreign currencies. These derivative contracts are not designated for hedge accounting treatment. As of June 30, 2020, the Company had open foreign exchange forward contracts with a notional U.S. dollar equivalent absolute value of $390.9 million. The following table displays the notional amounts of the most significant net foreign exchange hedge positions outstanding as of June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ Buy / (Sell) 2020 ​ Euro ​ $ (252.2) ​ Chinese Yuan ​ $ (56.1) ​ Swiss Franc ​ $ 25.7 ​ Korean Won ​ $ (14.5) ​ Mexican Peso ​ $ (12.4) ​ ​ Open foreign exchange forward contracts as of June 30, 2020 had maturities occurring over a period of two months. Foreign Exchange Cash Flow Hedges The Company also enters into forward contracts with the objective of managing the currency risk associated with forecasted U.S. dollar-denominated raw materials purchases by one of its subsidiaries whose functional currency is the euro. By entering into these forward contracts, which are designated as cash flow hedges, the Company buys a designated amount of U.S. dollars and sells euros at the prevailing market rate to mitigate the risk associated with the fluctuations in the euro-to-U.S. dollar foreign currency exchange rates. The qualifying hedge contracts are marked-to-market at each reporting date and any unrealized gains or losses are included in Accumulated Other Comprehensive Income (“AOCI”) to the extent effective, and reclassified to cost of sales in the period during which the transaction affects earnings or it becomes probable that the forecasted transaction will not occur. Open foreign exchange cash flow hedges as of June 30, 2020 had maturities occurring over a period of six months, and had a net notional U.S. dollar equivalent of $42.0 million. Interest Rate Swaps On September 6, 2017, the Company issued the 2024 Term Loan B, which currently bears an interest rate of LIBOR plus 2.00%, subject to a 0.00% LIBOR floor. In order to reduce the variability in interest payments associated with the Company’s variable rate debt, during 2017 the Company entered into certain interest rate swap agreements to convert a portion of these variable rate borrowings into a fixed rate obligation. These interest rate swap agreements are designated as cash flow hedges, and as such, the contracts are marked-to-market at each reporting date and any unrealized gains or losses are included in AOCI to the extent effective, and reclassified to interest expense in the period during which the transaction affects earnings or it becomes probable that the forecasted transaction will not occur. As of June 30, 2020, the Company had open interest rate swap agreements with a net notional U.S. dollar equivalent of $200.0 million which had an effective date of September 29, 2017 and mature in September 2022. Under the terms of the swap agreements, the Company is required to pay the counterparties a stream of fixed interest payments at a rate of 1.81%, and in turn, receives variable interest payments based on 1-month LIBOR (0.18% as of June 30, 2020) from the counterparties. Net Investment Hedge On September 1, 2017, the Company entered into certain fixed-for-fixed cross currency swaps (“CCS”), swapping USD principal and interest payments on its 2025 Senior Notes for euro-denominated payments. Under the terms of this CCS (the “2017 CCS”), the Company notionally exchanged $500.0 million at an interest rate of 5.375% for €420.0 million at a weighted average interest rate of 3.45% for approximately five years. On September 1, 2017, the Company designated the full notional amount of the 2017 CCS (€420.0 million) as a hedge of its net investment in certain European subsidiaries under the forward method, with all changes in the fair value of the 2017 CCS recorded as a component of AOCI, as the 2017 CCS were deemed to be highly effective hedges. A cumulative foreign currency translation loss of $38.0 million was recorded within AOCI related to the 2017 CCS through March 31, 2018. Effective April 1, 2018, the Company elected as an accounting policy to re-designate the 2017 CCS as a net investment hedge (and any future similar hedges) under the spot method. As such, changes in the fair value of the 2017 CCS included in the assessment of effectiveness (changes due to spot foreign exchange rates) were recorded as cumulative foreign currency translation within OCI, and will remain in AOCI until either the sale or substantially complete liquidation of the subsidiary. As of June 30, 2020, no gains or losses have been reclassified from AOCI into income related to the sale or substantially complete liquidation of the relevant subsidiaries. As an additional accounting policy election applied to similar hedges under this new standard, the initial value of any component excluded from the assessment of effectiveness is recognized in income using a systematic and rational method over the life of the hedging instrument. Any difference between the change in the fair value of the excluded component and amounts recognized in income under that systematic and rational method is recognized in AOCI. Prior to April 1, 2018, no components were excluded from the assessment of effectiveness for any of the Company’s existing net investment hedges. As of April 1, 2018, the initial excluded component value related to the 2017 CCS was $23.6 million, which the Company elected to amortize as a reduction of “Interest expense, net” in the condensed consolidated statements of operations using the straight-line method over the remaining term of the 2017 CCS. Additionally, the accrual of periodic USD and euro-denominated interest receipts and payments under the terms of the 2017 CCS were recognized within “Interest expense, net” in the condensed consolidated statements of operations. On February 26, 2020, the Company settled its 2017 CCS and replaced it with a new CCS arrangement (the “2020 CCS”) that carried substantially the same terms as the 2017 CCS. Upon settlement of the 2017 CCS, the Company realized net cash proceeds of $51.6 million. The remaining $13.8 million unamortized balance of the initial excluded component related to the 2017 CCS at the time of settlement is no longer being amortized following the settlement and will remain in AOCI until either the sale or substantially complete liquidation of the relevant subsidiaries. Under the 2020 CCS, the Company notionally exchanged $500.0 million at an interest rate of 5.375% for €459.3 million at a weighted average interest rate of 3.672% for approximately 2.7 years, with a final maturity of November 3, 2022. The cash flows under the 2020 CCS are aligned with the Company’s principal and interest obligations on its 5.375% 2025 Senior Notes. Summary of Derivative Instruments The following table presents the effect of the Company’s derivative instruments, including those not designated for hedge accounting treatment, on the condensed consolidated statements of operations for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Location and Amount of Gain (Loss) Recognized in ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ ​ June 30, 2020 ​ June 30, 2019 ​ ​ Cost of ​ Interest expense, net ​ Other expense, net ​ Cost of ​ Interest expense, net ​ Other expense, net Total amount of income and expense line items presented in the statements of operations in which the effects of derivative instruments are recorded ​ $ 576.8 ​ $ 11.7 ​ $ 1.0 ​ $ 865.6 ​ $ 9.9 ​ $ 1.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of cash flow hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain reclassified from AOCI into income ​ $ 0.5 ​ $ — ​ $ — ​ $ 1.6 ​ $ — ​ $ — ​ Interest rate swaps ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain (loss) reclassified from AOCI into income ​ $ — ​ $ (0.7) ​ $ — ​ $ — ​ $ 0.3 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of net investment hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain excluded from effectiveness testing ​ $ — ​ $ 2.0 ​ $ — ​ $ — ​ $ 3.9 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of derivatives not designated as hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange forward contracts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of loss recognized in income ​ $ — ​ $ — ​ $ (8.1) ​ $ — ​ $ — ​ $ (2.4) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Location and Amount of Gain (Loss) Recognized in ​ ​ Six Months Ended ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ June 30, 2019 ​ ​ Cost of Interest expense, net Other expense, net Cost of Interest expense, net Other expense, net Total amount of income and expense line items presented in the statements of operations in which the effects of derivative instruments are recorded ​ $ 1,360.6 ​ $ 22.0 ​ $ 2.6 ​ $ 1,781.2 ​ $ 20.1 ​ $ 5.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of cash flow hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain reclassified from AOCI into income ​ $ 0.6 ​ $ — ​ $ — ​ $ 2.2 ​ $ — ​ $ — ​ Interest rate swaps ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain (loss) reclassified from AOCI into income ​ $ — ​ $ (0.7) ​ $ — ​ $ — ​ $ 0.7 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of net investment hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain excluded from effectiveness testing (1) ​ $ — ​ $ 5.4 ​ $ — ​ $ — ​ $ 7.9 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of derivatives not designated as hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange forward contracts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain recognized in income ​ $ — ​ $ — ​ $ 5.7 ​ $ — ​ $ — ​ $ 0.3 ​ (1) Amount for the six months ended June 30, 2020 includes the effect on AOCI from the 2017 CCS through its settlement on February 26, 2020 and the effect on AOCI from the 2020 CCS from when it was entered into on February 26, 2020 through June 30, 2020. The following table presents the effect of cash flow and net investment hedge accounting on AOCI for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ` ​ Gain (Loss) Recognized in AOCI on Balance Sheet ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Designated as Cash Flow Hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges $ (1.2) $ (1.8) $ 0.9 $ 0.5 Interest rate swaps ​ ​ (0.1) ​ ​ (3.6) ​ ​ (5.9) ​ ​ (5.8) Total ​ $ (1.3) ​ $ (5.4) ​ $ (5.0) ​ $ (5.3) Designated as Net Investment Hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) (1) ​ $ (10.3) ​ $ (3.6) ​ $ 12.6 ​ $ 7.9 Total ​ $ (10.3) ​ $ (3.6) ​ $ 12.6 ​ $ 7.9 (1) Amount for the six months ended June 30, 2020 includes the effect on AOCI from the 2017 CCS through its settlement on February 26, 2020 and the effect on AOCI from the 2020 CCS from when it was entered into on February 26, 2020 through June 30, 2020. The Company recorded losses of $8.1 million and gains of $5.7 million during the three and six months ended June 30, 2020, respectively, and recorded losses of $2.4 million and gains of $0.3 million during the three and six months ended June 30, 2019, respectively, from settlements and changes in the fair value of outstanding forward contracts (not designated as hedges). The losses and gains from these forward contracts offset net foreign exchange transaction gains of $8.7 million and losses of $5.3 million during the three and six months ended June 30, 2020, respectively, and gains of $2.6 million and losses of $0.5 million during the three and six months ended June 30, 2019, respectively, which resulted from the re-measurement of the Company’s foreign currency denominated assets and liabilities. The cash settlements of these foreign exchange forward contracts are included within operating activities in the condensed consolidated statements of cash flows. The Company expects to reclassify in the next twelve months an approximate $2.9 million net loss from AOCI into earnings related to the Company’s outstanding foreign exchange cash flow hedges and interest rate swaps as of June 30, 2020 based on current foreign exchange rates. The following tables summarize the gross and net unrealized gains and losses, as well as the balance sheet classification, of outstanding derivatives recorded in the condensed consolidated balance sheets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Foreign ​ Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ Exchange ​ Interest ​ Cross ​ ​ ​ ​ Balance Sheet ​ Forward ​ Cash Flow ​ Rate ​ Currency ​ ​ ​ Classification Contracts ​ Hedges ​ Swaps ​ Swaps ​ Total ​ Asset Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable, net of allowance ​ $ 0.8 ​ $ 0.4 ​ $ — ​ $ 6.6 ​ $ 7.8 ​ Gross derivative asset position ​ ​ 0.8 ​ ​ 0.4 ​ ​ — ​ ​ 6.6 ​ ​ 7.8 ​ Less: Counterparty netting ​ ​ (0.6) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.6) ​ Net derivative asset position ​ $ 0.2 ​ $ 0.4 ​ $ — ​ $ 6.6 ​ $ 7.2 ​ Liability Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ (3.3) ​ $ — ​ $ (3.3) ​ $ — ​ $ (6.6) ​ Other noncurrent obligations ​ ​ — ​ ​ — ​ ​ (4.0) ​ ​ (13.5) ​ ​ (17.5) ​ Gross derivative liability position ​ ​ (3.3) ​ ​ — ​ ​ (7.3) ​ ​ (13.5) ​ ​ (24.1) ​ Less: Counterparty netting ​ ​ 0.6 ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.6 ​ Net derivative liability position ​ $ (2.7) ​ $ — ​ $ (7.3) ​ $ (13.5) ​ $ (23.5) ​ Total net derivative position ​ $ (2.5) ​ $ 0.4 ​ $ (7.3) ​ $ (6.9) ​ $ (16.3) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Foreign ​ Foreign ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ Exchange ​ Interest ​ Cross ​ ​ ​ ​ Balance Sheet ​ Forward ​ Cash Flow ​ Rate ​ Currency ​ ​ Classification Contracts Hedges Swaps Swaps Total Asset Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable, net of allowance ​ $ 1.1 ​ $ — ​ $ — ​ $ 8.6 ​ $ 9.7 ​ Deferred charges and other assets ​ ​ — ​ ​ — ​ ​ — ​ ​ 19.2 ​ ​ 19.2 ​ Gross derivative asset position ​ ​ 1.1 ​ ​ — ​ ​ — ​ ​ 27.8 ​ ​ 28.9 ​ Less: Counterparty netting ​ ​ (0.4) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.4) ​ Net derivative asset position ​ $ 0.7 ​ $ — ​ $ — ​ $ 27.8 ​ $ 28.5 ​ Liability Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ (5.7) ​ $ (0.5) ​ $ (0.4) ​ $ — ​ $ (6.6) ​ Other noncurrent obligations ​ ​ — ​ ​ — ​ ​ (1.0) ​ ​ — ​ ​ (1.0) ​ Gross derivative liability position ​ ​ (5.7) ​ ​ (0.5) ​ ​ (1.4) ​ ​ — ​ ​ (7.6) ​ Less: Counterparty netting ​ ​ 0.5 ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.5 ​ Net derivative liability position ​ $ (5.2) ​ $ (0.5) ​ $ (1.4) ​ $ — ​ $ (7.1) ​ Total net derivative position ​ $ (4.5) ​ $ (0.5) ​ $ (1.4) ​ $ 27.8 ​ $ 21.4 ​ ​ Forward contracts, interest rate swaps, and cross currency swaps are entered into with a limited number of counterparties, each of which allows for net settlement of all contracts through a single payment in a single currency in the event of a default on or termination of any one contract. As such, in accordance with the Company’s accounting policy, these derivative instruments are recorded on a net basis by counterparty within the condensed consolidated balance sheets. Refer to Notes 9 and 17 of the condensed consolidated financial statements for further information regarding the fair value of the Company’s derivative instruments and the related changes in AOCI.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Measurements
Fair Value Measurements	NOTE 9—FAIR VALUE MEASUREMENTS Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Assets and liabilities measured at fair value are classified using the following hierarchy, which is based upon the transparency of inputs to the valuation as of the measurement date. Level 1—Valuation is based upon quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2—Valuation is based upon quoted prices for similar assets and liabilities in active markets, or other inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the financial instrument. Level 3—Valuation is based upon other unobservable inputs that are significant to the fair value measurement. The following table summarizes the basis used to measure certain assets and liabilities at fair value on a recurring basis in the condensed consolidated balance sheets as of June 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ Assets (Liabilities) at Fair Value (Level 1) (Level 2) (Level 3) Total Foreign exchange forward contracts—Assets $ — $ 0.2 $ — $ 0.2 ​ Foreign exchange forward contracts—(Liabilities) ​ — ​ (2.7) ​ — ​ (2.7) ​ Foreign exchange cash flow hedges—Assets ​ ​ — ​ ​ 0.4 ​ ​ — ​ ​ 0.4 ​ Interest rate swaps—(Liabilities) ​ ​ — ​ ​ (7.3) ​ ​ — ​ ​ (7.3) ​ Cross currency swaps—Assets ​ ​ — ​ ​ 6.6 ​ ​ — ​ ​ 6.6 ​ Cross currency swaps—(Liabilities) ​ ​ — ​ ​ (13.5) ​ ​ — ​ ​ (13.5) ​ Total fair value ​ $ — ​ $ (16.3) ​ $ — ​ $ (16.3) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ Assets (Liabilities) at Fair Value (Level 1) (Level 2) (Level 3) Total Foreign exchange forward contracts—Assets ​ $ — $ 0.7 $ — $ 0.7 ​ Foreign exchange forward contracts—(Liabilities) ​ ​ — ​ ​ (5.2) ​ ​ — ​ ​ (5.2) ​ Foreign exchange cash flow hedges—(Liabilities) ​ ​ — ​ ​ (0.5) ​ ​ — ​ ​ (0.5) ​ Interest rate swaps—(Liabilities) ​ ​ — ​ ​ (1.4) ​ ​ — ​ ​ (1.4) ​ Cross currency swaps—Assets ​ ​ — ​ ​ 27.8 ​ ​ — ​ ​ 27.8 ​ Total fair value ​ $ — ​ $ 21.4 ​ $ — ​ $ 21.4 ​ ​ The Company uses an income approach to value its derivative instruments, utilizing discounted cash flow techniques, considering the terms of the contract and observable market information available as of the reporting date, such as interest rate yield curves and currency spot and forward rates. Significant inputs to the valuation for these derivative instruments are obtained from broker quotations or from listed or over-the-counter market data, and are classified as Level 2 in the fair value hierarchy. Nonrecurring Fair Value Measurements The Company’s financial assets measured at fair value on a nonrecurring basis as of June 30, 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ ​ ​ (Level 1) (Level 2) (Level 3) Total ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Boehlen styrene monomer property, plant and equipment ​ $ — ​ $ — ​ $ 3.3 ​ $ 3.3 ​ Schkopau PBR property, plant and equipment ​ ​ — ​ ​ — ​ ​ 1.5 ​ ​ 1.5 ​ Total fair value ​ $ — ​ $ — ​ $ 4.8 ​ $ 4.8 ​ ​ In 2020, the Company continued its strategy to focus efforts and increase investments in certain product offerings serving the following applications, which are less cyclical and offer significantly higher growth and margin potential: coatings, adhesives, sealants, and elastomers applications (“CASE”) within the Latex Binders segment; engineered materials applications within the Performance Plastics segment; and solution styrene butadiene rubber (“SSBR”) within the Synthetic Rubber segment. As a result of continuing this strategy and other management considerations, in March of 2020, the Company initiated a consultation process with the Economic Council and Works Councils of Trinseo Deutschland regarding the disposition of its styrene monomer assets in Boehlen, Germany and its polybutadiene rubber (“PBR,” specifically nickel and neodymium-PBR) assets in Schkopau, Germany. Based on the Company’s evaluation of these asset groups, it determined that the long-lived assets at both locations should be assessed for impairment during the six months ended June 30, 2020. These assessments indicated that the carrying values of the asset groups at each location were not recoverable when compared to the expected undiscounted future cash flows from the operation and potential disposition of these assets. Based upon the Company’s assessment, it concluded that the fair value of the Boehlen styrene monomer and Schkopau PBR asset groups totaled $3.3 million and $1.5 million, respectively, as of June 30, 2020, including the impacts of depreciation and foreign currency during the three months ended June 30, 2020. Therefore, the Company recorded impairment charges on the Boehlen styrene monomer assets and the Schkopau PBR assets of $10.3 million and $28.0 million, respectively, during the six months ended June 30, 2020, which are included within “Impairment charges” on the condensed consolidated statements of operations. The fair value of the depreciable assets at each location was determined through an analysis of the underlying fixed asset records in conjunction with the use of industry experience and available market data. There were no other financial assets and no financial liabilities measured at fair value on a nonrecurring basis as of June 30, 2020 and there were no financial assets or liabilities measured at fair value on a nonrecurring basis as of December 31, 2019. Fair Value of Debt Instruments The following table presents the estimated fair value of the Company’s outstanding debt not carried at fair value as of June 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ June 30, 2020 December 31, 2019 2025 Senior Notes ​ $ 476.1 ​ $ 503.7 ​ 2024 Term Loan B ​ ​ 650.2 ​ ​ 686.4 ​ Total fair value ​ $ 1,126.3 ​ $ 1,190.1 ​ ​ The fair value of the Company’s debt facilities above (each Level 2 securities) is determined using over-the-counter market quotes and benchmark yields received from independent vendors. There were no other significant financial instruments outstanding as of June 30, 2020 and December 31, 2019.

Provision for Income Taxes

Provision for Income Taxes	6 Months Ended
	Jun. 30, 2020
Provision for Income Taxes
Income Taxes	NOTE 10—PROVISION FOR INCOME TAXES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 2019 2020 2019 ​ Effective income tax rate ​ ​ (101.5) % ​ 36.0 % ​ (47.2) % ​ 29.3 % ​ ​ Provision for income taxes for the three and six months ended June 30, 2020 totaled $64.7 million and $52.8 million, respectively, resulting in an effective tax rate of (101.5)% and (47.2)%, respectively. Provision for income taxes for the three and six months ended June 30, 2019 totaled $15.7 million and $26.5 million, respectively, resulting in an effective tax rate of 36.0% and 29.3%, respectively. The effective income tax rate for the three and six months ended June 30, 2020 was primarily driven by the Company’s forecasted jurisdictional mix of earnings, where the tax benefit of losses expected to be generated in lower rate jurisdictions are being more than offset by tax expense on income expected to be generated in higher tax jurisdictions, resulting in a negative tax rate based on the overall forecasted loss for the year. Also impacting the rate for the six months ended June 30, 2020 was a tax benefit related to the impairment charges recorded during the period related to the Company’s assets in Boehlen and Schkopau, Germany. Refer to Note 9 in the condensed consolidated financial statements for further information.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure
Commitments and Contingencies	NOTE 11—COMMITMENTS AND CONTINGENCIES Environmental Matters Accruals for environmental matters are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated based on current law, existing technologies and other information. Pursuant to the terms of the agreement associated with the Company’s formation, the pre-closing environmental liabilities were retained by Dow, and Dow agreed, subject to temporal, monetary, and other limitations to indemnify the Company from and against environmental liabilities incurred or relating to the predecessor periods. No environmental claims have been asserted or threatened against the Company, and the Company is not a potentially responsible party at any Superfund Sites. As of June 30, 2020 and December 31, 2019, the Company had no accrued obligations for environmental remediation or restoration costs. Inherent uncertainties exist in the Company’s potential environmental liabilities primarily due to unknown conditions, whether future claims may fall outside the scope of the indemnity, changing governmental regulations and legal standards regarding liability, and evolving technologies for handling site remediation and restoration. In connection with the Company’s existing indemnification, the possibility is considered remote that environmental remediation costs will have a material adverse impact on the condensed consolidated financial statements over the next 12 months. Purchase Commitments In the normal course of business, the Company has certain raw material purchase contracts where it is required to purchase certain minimum volumes at current market prices. These commitments range from one Litigation Matters From time to time, the Company may be subject to various legal claims and proceedings incidental to the normal conduct of business, relating to such matters as employees, product liability, antitrust/competition, past waste disposal practices and release of chemicals into the environment. While it is impossible at this time to determine with certainty the ultimate outcome of these routine claims, the Company does not believe that the ultimate resolution of these claims will have a material adverse effect on the Company’s results of operations, financial condition or cash flow. Legal costs, including those legal costs expected to be incurred in connection with a loss contingency, are expensed as incurred. European Commission Request for Information On June 6, 2018, Trinseo Europe GmbH, a subsidiary of the Company, received a Request for Information in the form of a letter from the European Commission Directorate General for Competition (the “European Commission”) related to styrene monomer commercial activity in the European Economic Area. The Company subsequently commenced an internal investigation into these commercial activities and discovered instances of inappropriate activity. On October 28, 2019, a supplemental request for information was received from the European Commission. This request was limited to historical employment, entity, and organizational structures, along with certain financial, styrene purchasing, and styrene market information, as well as certain spot styrene purchase contracts. The Company has provided this information and continues to fully cooperate with the European Commission. The proceedings with the European Commission continue and its outcome remains open. Based on its findings, the European Commission may decide to: (i) require further information; (ii) conduct unannounced raids of the Company’s premises; (iii) adopt a decision imposing fines, and/or request certain behavioral or structural commitments from the Company; or (iv) in view of defense arguments by the Company close the proceedings. As a result of the above factors, the Company is unable to predict the ultimate outcome of this matter or estimate the range of reasonably possible losses that could be incurred. However, any potential losses incurred could be material to the Company’s results of operations, balance sheet, and cash flows for the period in which they are resolved or become probable and reasonably estimable.

Pension Plans and Other Postret

Pension Plans and Other Postretirement Benefits	6 Months Ended
	Jun. 30, 2020
Pension Plans and Other Postretirement Benefits
Pension Plans and Other Postretirement Benefits	NOTE 12—PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS The components of net periodic benefit costs for all significant plans were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Defined Benefit Pension Plans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Service cost ​ $ 4.2 ​ $ 3.1 $ 8.6 ​ $ 6.3 ​ Interest cost ​ 0.8 ​ 1.2 ​ 1.6 ​ 2.5 ​ Expected return on plan assets ​ (0.3) ​ (0.5) ​ (0.6) ​ (1.0) ​ Amortization of prior service credit ​ (0.3) ​ (0.3) ​ (0.6) ​ (0.5) ​ Amortization of net loss ​ 1.2 ​ 0.8 ​ 2.3 ​ 1.5 ​ Net settlement loss ​ — ​ — ​ — ​ 0.7 ​ Net periodic benefit cost ​ $ 5.6 ​ $ 4.3 ​ $ 11.3 ​ $ 9.5 ​ ​ The Company had less than $0.1 million of net periodic benefit costs for its other postretirement plans for the three and six months ended June 30, 2020 and 2019. Service cost related to the Company’s defined benefit pension plans and other postretirement plans is included within “Cost of sales” and “Selling, general and administrative expenses” whereas all other components of net periodic benefit cost are included within “Other expense, net” in the condensed consolidated statements of operations. As of June 30, 2020 and December 31, 2019, the Company’s benefit obligations included primarily in “Other noncurrent obligations” in the condensed consolidated balance sheets were $276.0 million and $270.6 million, respectively. The Company made cash contributions and benefit payments to unfunded plans of approximately $1.6 million and $3.4 million during the three and six months ended June 30, 2020, respectively. The Company expects to make additional cash contributions, including benefit payments to unfunded plans, of approximately $4.5 million to its defined benefit plans for the remainder of 2020.

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	NOTE 13—SHARE-BASED COMPENSATION Refer to the Annual Report for definitions of capitalized terms not included herein and further background on the Company’s share-based compensation programs included in the tables below. The following table summarizes the Company’s share-based compensation expense for the three and six months ended June 30, 2020 and 2019, as well as unrecognized compensation cost as of June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ Three Months Ended ​ Six Months Ended June 30, 2020 ​ ​ ​ June 30, ​ June 30, Unrecognized ​ Weighted ​ ​ 2020 2019 2020 2019 Compensation Cost Average Years ​ RSUs ​ $ 1.8 ​ $ 1.9 ​ $ 3.5 ​ $ 4.0 $ 12.3 ​ 2.0 ​ Options ​ ​ 0.8 ​ ​ 0.8 ​ ​ 1.8 ​ ​ 2.0 ​ 2.7 ​ 1.4 ​ PSUs ​ ​ 0.5 ​ ​ 0.8 ​ ​ 1.0 ​ ​ 1.7 ​ 3.7 ​ 2.1 ​ Total share-based compensation expense ​ $ 3.1 ​ $ 3.5 ​ $ 6.3 ​ $ 7.7 ​ ​ ​ ​ ​ ​ The following table summarizes awards granted and the respective weighted average grant date fair value for the six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ ​ ​ Awards Granted ​ Weighted Average Grant Date Fair Value per Award ​ RSUs ​ ​ 355,818 ​ $ 24.13 ​ Options ​ ​ 530,241 ​ ​ 6.51 ​ PSUs ​ ​ 102,545 ​ ​ 24.54 ​ ​ Option Awards The following are the weighted average assumptions used within the Black-Scholes pricing model for the Company’s option awards granted during the six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, 2020 ​ Expected term (in years) 5.50 ​ Expected volatility 39.93 % Risk-free interest rate 1.19 % Dividend yield ​ 3.25 % ​ The expected volatility assumption is predominantly determined based on the historical volatility of the Company’s publicly traded ordinary shares. The expected term of option awards represents the period of time that option awards granted are expected to be outstanding. For the option awards granted during the six months ended June 30, 2020, the simplified method was used to calculate the expected term, given the Company’s limited historical exercise data. The risk-free interest rate for the periods within the expected term of option awards is based on the U.S. Treasury yield curve in effect at the time of grant. The dividend yield is estimated based on historical and expected dividend activity. Performance Share Units (PSUs) The following are the weighted average assumptions used within the Monte Carlo valuation model for PSUs granted during the six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ Expected term (in years) ​ 3.00 ​ Expected volatility 40.50 % Risk-free interest rate 1.16 % Share price $ 24.30 ​ ​ Determining the fair value of PSUs requires considerable judgment, including estimating the expected volatility of the price of the Company’s ordinary shares, the correlation between the Company’s share price and that of its peer companies, and the expected rate of interest. The expected volatility for each grant is determined based on the historical volatility of the Company’s ordinary shares. The expected term of PSUs represents the length of the performance period. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for a duration equivalent to the performance period. The share price is the closing price of the Company’s ordinary shares on the grant date.

Acquisitions and Divestitures

Acquisitions and Divestitures	6 Months Ended
	Jun. 30, 2020
Acquisitions and Divestitures
Acquisitions and Divestitures	NOTE 14—ACQUISITIONS AND DIVESTITURES Acquisition of Latex Binders Assets in Germany On October 1, 2019, the Company completed the acquisition from Dow of its latex binder production facilities and related infrastructure in Rheinmünster, Germany. The transaction included full ownership and operational control of latex production facilities, site infrastructure, and service contracts, as well as certain employees transferring from Dow to Trinseo. This acquisition provided Trinseo with manufacturing assets supporting its strategy to grow its Latex Binders business in applications serving the coatings, adhesives, specialty paper, and sealants markets. The transaction was accounted for as a business combination and did not require any upfront cash outlay from Trinseo. The Company assumed net liabilities of $2.0 million as well as employees transferred in connection with the acquisition during the year ended December 31, 2019. In exchange for the net liabilities assumed, Trinseo received net cash of $6.7 million during the year ended December 31, 2019, and an additional $0.2 million during the six months ended June 30, 2020. The Company allocated the purchase price of the acquisition to identifiable assets acquired and liabilities assumed based on their estimated fair values as of the acquisition date. During the second quarter of 2020, there were no changes to the purchase price allocation for the acquisition. However, further adjustments may be necessary as a result of the Company’s ongoing assessment of additional information related to the fair value of assets acquired and liabilities assumed during the measurement period. Refer to the Annual Report for further information.

Segments

Segments	6 Months Ended
	Jun. 30, 2020
Segments
Segments	NOTE 15—SEGMENTS The Company operates under six segments: Latex Binders, Synthetic Rubber, Performance Plastics, Polystyrene, Feedstocks, and Americas Styrenics. The Latex Binders segment produces styrene-butadiene latex (“SB latex”) and other latex polymers and binders, primarily for coated paper and packaging board, carpet and artificial turf backings, as well as a broad range of performance latex binders products, including SB latex, SA latex, and vinylidene chloride latex for CASE applications. The Synthetic Rubber segment produces synthetic rubber products, including SSBR, used predominantly in high-performance tires, impact modifiers and technical rubber products, such as conveyer belts, hoses, seals and gaskets. The Performance Plastics segment includes a variety of highly engineered compounds and blends, the Company’s acrylonitrile-butadiene-styrene (“ABS”), styrene-acrylonitrile (“SAN”), and polycarbonate (“PC”) businesses, and engineered materials applications, which includes consumer electronics, medical, and thermoplastic elastomers (“TPEs”) applications. The Polystyrene segment includes a variety of general purpose polystyrenes (“GPPS”) and polystyrene that has been modified with polybutadiene rubber to increase its impact resistant properties (“HIPS”). The Feedstocks segment includes the Company’s production and procurement of styrene monomer outside of North America, which is used as a key raw material in many of the Company’s products, including polystyrene, SB latex, ABS resins, and SSBR. Lastly, the Americas Styrenics segment consists solely of the operations of the Company’s 50%-owned joint venture, Americas Styrenics, a producer of both styrene monomer and polystyrene in North America. The following table provides disclosure of the Company’s segment Adjusted EBITDA, which is used to measure segment operating performance and is defined below, for the three and six months ended June 30, 2020 and 2019. Asset and intersegment sales information by reporting segment is not regularly reviewed or included with the Company’s reporting to the chief operating decision maker. Therefore, this information has not been disclosed below. Refer to Note 3 for the Company’s net sales to external customers by segment for the three and six months ended June 30, 2020 and 2019. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas Three Months Ended (1) ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Styrenics June 30, 2020 $ 17.0 $ (27.7) $ (5.6) ​ $ 14.8 $ (3.5) $ 14.4 ​ June 30, 2019 ​ $ 20.6 ​ $ 12.9 ​ $ 34.2 ​ $ 16.2 ​ $ (0.6) ​ $ 40.3 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas Six Months Ended (1) ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Styrenics June 30, 2020 $ 38.6 ​ $ (12.5) ​ $ 31.2 ​ $ 26.6 ​ $ (19.8) ​ $ 24.2 ​ June 30, 2019 ​ $ 38.1 ​ $ 21.7 ​ $ 69.9 ​ $ 32.9 ​ $ 16.6 ​ $ 72.5 ​ (1) The Company’s primary measure of segment operating performance is Adjusted EBITDA, which is defined as income from continuing operations before interest expense, net; provision for income taxes; depreciation and amortization expense; loss on extinguishment of long-term debt; asset impairment charges; gains or losses on the dispositions of businesses and assets; restructuring charges; acquisition related costs and benefits and other items. Segment Adjusted EBITDA is a key metric that is used by management to evaluate business performance in comparison to budgets, forecasts, and prior year financial results, providing a measure that management believes reflects core operating performance by removing the impact of transactions and events that would not be considered a part of core operations. Other companies in the industry may define segment Adjusted EBITDA differently than the Company, and as a result, it may be difficult to use segment Adjusted EBITDA, or similarly named financial measures, that other companies may use to compare the performance of those companies to the Company’s segment performance. ​ The reconciliation of income before income taxes to segment Adjusted EBITDA is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Income (loss) before income taxes ​ $ (63.7) ​ $ 43.7 ​ $ (111.9) ​ $ 90.3 ​ Interest expense, net ​ 11.7 ​ 9.9 ​ 22.0 ​ 20.1 ​ Depreciation and amortization ​ 34.8 ​ 34.7 ​ ​ 71.1 ​ 68.7 ​ Corporate Unallocated (2) ​ ​ 17.7 ​ ​ 20.8 ​ ​ 39.6 ​ ​ 46.9 ​ Adjusted EBITDA Addbacks (3) ​ 8.9 ​ 14.5 ​ 67.5 ​ 25.7 ​ Segment Adjusted EBITDA ​ $ 9.4 ​ $ 123.6 ​ $ 88.3 ​ $ 251.7 ​ (2) Corporate unallocated includes corporate overhead costs and certain other income and expenses. (3) Adjusted EBITDA addbacks for the three and six months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 2019 2020 2019 Net gain on disposition of businesses and assets ​ $ — ​ $ — ​ $ (0.4) ​ $ (0.2) ​ Restructuring and other charges (Note 16) ​ ​ 6.3 ​ ​ (0.3) ​ ​ 8.1 ​ ​ 0.1 ​ Acquisition transaction and integration net costs ​ ​ (0.4) ​ ​ 0.7 ​ ​ (0.3) ​ ​ 0.7 ​ Asset impairment charges or write-offs (Note 9) ​ ​ — ​ ​ — ​ ​ 38.3 ​ ​ — ​ Other items (a) ​ ​ 3.0 ​ ​ 14.1 ​ ​ 21.8 ​ ​ 25.1 ​ Total Adjusted EBITDA Addbacks ​ $ 8.9 ​ $ 14.5 ​ $ 67.5 ​ $ 25.7 ​ (a) Other items for the three and six months ended June 30, 2020 and 2019 primarily relate to advisory and professional fees incurred in conjunction with the Company’s initiative to transition business services from Dow, including certain administrative services such as accounts payable, logistics, finance, and IT services. Also included within other items for the three and six months ended June 30, 2020 and 2019 are fees incurred in conjunction with certain of the Company’s strategic initiatives.

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2020
Restructuring
Restructuring	NOTE 16—RESTRUCTURING Refer to the Annual Report for further details regarding the Company’s previously announced restructuring activities included in the tables below. Restructuring charges are included within “Selling, general and administrative expenses” in the condensed consolidated statements of operations. The following table provides detail of the Company’s restructuring charges for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ Cumulative ​ ​ ​ ​ ​ June 30, ​ June 30, ​ Life-to-date ​ ​ ​ ​ ​ 2020 2019 ​ 2020 2019 ​ Charges Segment ​ Corporate Restructuring Program ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accelerated depreciation ​ $ 1.2 ​ $ — ​ $ 2.5 ​ $ — ​ $ 2.9 ​ ​ ​ Employee termination benefits ​ ​ 4.1 ​ ​ — ​ ​ 4.4 ​ ​ — ​ ​ 21.4 ​ ​ ​ Contract terminations ​ ​ 1.2 ​ ​ — ​ ​ 2.4 ​ ​ — ​ ​ 2.8 ​ ​ ​ Corporate Program Subtotal ​ $ 6.5 ​ $ — ​ $ 9.3 ​ $ — ​ $ 27.1 ​ N/A (1) ​ Terneuzen Compounding Restructuring ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset impairment/accelerated depreciation ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 3.1 ​ ​ ​ Employee termination benefits ​ ​ — ​ ​ (0.4) ​ ​ — ​ ​ (0.4) ​ ​ 0.7 ​ ​ ​ Contract terminations ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.3 ​ ​ ​ Decommissioning and other ​ ​ 0.1 ​ ​ — ​ ​ 0.2 ​ ​ 0.2 ​ ​ 2.2 ​ ​ ​ Terneuzen Subtotal ​ $ 0.1 ​ $ (0.4) ​ $ 0.2 ​ $ (0.2) ​ $ 6.3 ​ Performance Plastics (2) ​ Livorno Plant Restructuring ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset impairment/accelerated depreciation ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 14.7 ​ ​ ​ Employee termination benefits ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 5.4 ​ ​ ​ Contract terminations ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.3 ​ ​ ​ Decommissioning and other ​ ​ — ​ ​ 0.1 ​ ​ 0.2 ​ ​ 0.3 ​ ​ 4.4 ​ ​ ​ Livorno Subtotal ​ $ — ​ $ 0.1 ​ $ 0.2 ​ $ 0.3 ​ $ 24.8 ​ Latex Binders (3) ​ Other Restructurings ​ ​ 0.9 ​ ​ — ​ ​ 0.9 ​ ​ — ​ ​ ​ ​ Various ​ Total Restructuring Charges ​ $ 7.5 ​ $ (0.3) ​ $ 10.6 ​ $ 0.1 ​ ​ ​ ​ ​ ​ (1) In November 2019, the Company announced a corporate restructuring program associated with the Company’s shift to a global functional structure and business excellence initiatives to drive greater focus on business process optimization and efficiency, which continued through the six months ended June 30, 2020. In connection with this restructuring plan, the Company incurred employee termination benefit charges of $4.1 million, inclusive of a share-based compensation benefit of $1.4 million, contract termination charges of $1.2 million, and accelerated depreciation charges of $1.2 million during the three months ended June 30, 2020. Employee termination benefit charges of $4.4 million, contract termination charges of $2.4 million, and accelerated depreciation charges of $2.5 million were incurred during the six months ended June 30, 2020. The Company expects to incur incremental employee termination benefit charges of less than $1.0 million, inclusive of pension charges, through the end of 2020, and the majority of these total benefits are expected to be paid by the end of 2020. As this was identified as a corporate-related activity, the charges related to this restructuring program were not allocated to a specific segment, but rather included within corporate unallocated. (2) In 2017, the Company announced plans to upgrade its production capability for compounded resins with the construction of a new state-of-the art compounding facility to replace its existing compounding facility in Terneuzen, The Netherlands. As of June 30, 2020, the new facility is complete, along with all substantive transition and quality assurance activities. Production at the prior facility ceased and decommissioning activities began in 2019, and are expected to continue through the first half of 2021. The Company estimates it will incur incremental decommissioning and other charges of less than $1.0 million through 2021, the majority of which are expected to be paid during the remainder of 2020. (3) In 2016, the Company ceased manufacturing activities at its latex binders manufacturing facility in Livorno, Italy and began decommissioning activities. In 2018, the Company entered into an agreement to sell the land where the former facility is located. This land sale closed in January 2020, for a total purchase price of $12.5 million. A prepayment of $1.3 million of this purchase price was received in 2018, and was recorded within “Accrued expenses and other current liabilities” on the condensed consolidated balance sheets as of December 31, 2019. The remaining purchase price was received in January 2020 when the transaction closed. The Company recorded a net gain on sale of $0.6 million during the six months ended June 30, 2020, which was recorded within “Selling, general and administrative expenses” in the condensed consolidated statements of operations. The following table provides a roll forward of the liability balances associated with the Company’s restructuring activities as of June 30, 2020. Employee termination benefit and contract termination charges are primarily recorded within “Accrued expenses and other current liabilities” in the condensed consolidated balance sheets. The liability balances as of June 30, 2020 primarily represent activity related to the corporate restructuring program. No other individual restructuring activity had a material liability balance as of June 30, 2020. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ December 31, 2019 Expenses Deductions (1) June 30, 2020 Employee termination benefits ​ $ 17.2 ​ $ 6.7 ​ $ (7.0) ​ $ 16.9 ​ Contract terminations ​ ​ 0.7 ​ ​ — ​ ​ (0.5) ​ ​ 0.2 ​ Decommissioning and other ​ — ​ 0.4 ​ (0.4) ​ — ​ Total ​ $ 17.9 ​ $ 7.1 ​ $ (7.9) ​ $ 17.1 ​ (1) Primarily includes payments made against the existing accrual, as well as immaterial impacts of foreign currency remeasurement.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 30, 2020
Shareholders' Equity.
Accumulated Other Comprehensive Income (Loss)	NOTE 17—ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The components of AOCI, net of income taxes, consisted of: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative Pension & Other ​ ​ ​ ​ ​ ​ ​ ​ Translation ​ Postretirement Benefit ​ ​ Cash Flow ​ ​ ​ ​ Three Months Ended June 30, 2020 and 2019 Adjustments Plans, Net ​ Hedges, Net Total Balance as of March 31, 2020 ​ $ (96.0) ​ $ (55.1) ​ $ (3.1) ​ $ (154.2) ​ Other comprehensive loss ​ (1.1) ​ — ​ (1.5) ​ (2.6) ​ Amounts reclassified from AOCI to net income (1) ​ ​ — ​ ​ 0.5 ​ ​ 0.2 ​ ​ 0.7 ​ Balance as of June 30, 2020 ​ $ (97.1) ​ $ (54.6) ​ $ (4.4) ​ $ (156.1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of March 31, 2019 ​ $ (112.1) ​ $ (40.4) ​ $ 9.0 ​ $ (143.5) ​ Other comprehensive income (loss) ​ 3.0 ​ — ​ (3.5) ​ (0.5) ​ Amounts reclassified from AOCI to net income (loss) (1) ​ ​ — ​ ​ 0.3 ​ ​ (1.9) ​ ​ (1.6) ​ Balance as of June 30, 2019 ​ $ (109.1) ​ $ (40.1) ​ $ 3.6 ​ $ (145.6) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative Pension & Other ​ ​ ​ ​ ​ ​ ​ Translation ​ Postretirement Benefit ​ Cash Flow ​ ​ ​ ​ Six Months Ended June 30, 2020 and 2019 ​ Adjustments Plans, Net Hedges, Net Total ​ Balance as of December 31, 2019 ​ $ (106.7) ​ $ (56.3) ​ $ 0.6 ​ $ (162.4) ​ Other comprehensive income (loss) ​ 9.6 ​ 0.6 ​ (5.1) ​ 5.1 ​ Amounts reclassified from AOCI to net income (1) ​ ​ — ​ ​ 1.1 ​ ​ 0.1 ​ ​ 1.2 ​ Balance as of June 30, 2020 ​ $ (97.1) ​ $ (54.6) ​ $ (4.4) ​ $ (156.1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of December 31, 2018 ​ $ (111.8) ​ $ (39.4) ​ $ 8.9 ​ $ (142.3) ​ Other comprehensive income (loss) ​ 2.7 ​ (2.0) ​ (2.4) ​ (1.7) ​ Amounts reclassified from AOCI to net income (loss) (1) ​ ​ — ​ ​ 1.3 ​ ​ (2.9) ​ ​ (1.6) ​ Balance as of June 30, 2019 ​ $ (109.1) ​ $ (40.1) ​ $ 3.6 ​ $ (145.6) ​ (1) The following is a summary of amounts reclassified from AOCI to net income for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ AOCI Components ​ June 30, ​ June 30, ​ Statements of Operations ​ ​ 2020 2019 2020 2019 Classification ​ Cash flow hedging items ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ $ (0.5) ​ $ (1.6) ​ $ (0.6) ​ $ (2.2) ​ Cost of sales ​ Interest rate swaps ​ ​ 0.7 ​ ​ (0.3) ​ ​ 0.7 ​ ​ (0.7) ​ Interest expense, net ​ Total before tax ​ ​ 0.2 ​ ​ (1.9) ​ ​ 0.1 ​ ​ (2.9) ​ ​ ​ Tax effect ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Provision for income taxes ​ Total, net of tax ​ $ 0.2 ​ $ (1.9) ​ $ 0.1 ​ $ (2.9) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of pension and other postretirement benefit plan items ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prior service credit ​ $ (0.3) ​ $ (0.3) ​ $ (0.6) ​ $ (0.6) ​ (a) ​ Net actuarial loss ​ ​ 1.1 ​ ​ 0.8 ​ ​ 2.3 ​ ​ 1.6 ​ (a) ​ Net settlement loss ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.7 ​ (a) ​ Total before tax ​ ​ 0.8 ​ ​ 0.5 ​ ​ 1.7 ​ ​ 1.7 ​ ​ ​ Tax effect ​ ​ (0.3) ​ ​ (0.2) ​ ​ (0.6) ​ ​ (0.4) ​ Provision for income taxes ​ Total, net of tax ​ $ 0.5 ​ $ 0.3 ​ $ 1.1 ​ $ 1.3 ​ ​ ​ (a) These AOCI components are included in the computation of net periodic benefit costs (see Note 12). ​

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share
Earnings Per Share	NOTE 18—EARNINGS PER SHARE Basic earnings per ordinary share (“basic EPS”) is computed by dividing net income available to ordinary shareholders by the weighted average number of the Company’s ordinary shares outstanding for the applicable period. Diluted earnings per ordinary share (“diluted EPS”) is calculated using net income available to ordinary shareholders divided by diluted weighted average ordinary shares outstanding during each period, which includes unvested RSUs, option awards, and PSUs. Diluted EPS considers the impact of potentially dilutive securities except in periods in which there is a loss because the inclusion of the potential ordinary shares would have an anti-dilutive effect. The following table presents basic EPS and diluted EPS for the three and six months ended June 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (in millions, except per share data) 2020 2019 2020 2019 Earnings: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (128.4) ​ $ 28.0 ​ $ (164.7) ​ $ 63.8 ​ Shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average ordinary shares outstanding ​ 38.2 ​ 40.8 ​ 38.4 ​ 41.0 ​ Dilutive effect of RSUs, option awards, and PSUs (1) ​ — ​ 0.3 ​ — ​ 0.5 ​ Diluted weighted average ordinary shares outstanding ​ 38.2 ​ 41.1 ​ 38.4 ​ 41.5 ​ Income (loss) per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) per share—basic ​ $ (3.36) ​ $ 0.69 ​ $ (4.29) ​ $ 1.56 ​ Income (loss) per share—diluted ​ $ (3.36) ​ $ 0.68 ​ $ (4.29) ​ $ 1.54 ​ (1) Refer to Note 13 for discussion of RSUs, option awards, and PSUs granted to certain Company directors and employees. As the Company recorded a net loss for the three and six months ended June 30, 2020, potential shares related to equity-based awards have been excluded from the calculation of diluted EPS, as doing so would be anti-dilutive. The number of anti-dilutive shares that have been excluded from the computation of diluted earnings per share were 0.7 million and 0.8 million for the three and six months ended June 30, 2019, respectively.

Basis of Presentation (Policies

Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2020
Basis of Presentation
Basis of Presentation	The unaudited interim condensed consolidated financial statements of Trinseo S.A. and its subsidiaries (the “Company”) as of and for the periods ended June 30, 2020 and 2019 were prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and reflect all adjustments, consisting only of normal recurring adjustments, which, in the opinion of management, are considered necessary for the fair statement of the results for the periods presented. Because they cover interim periods, the statements and related notes to the financial statements do not include all disclosures normally provided in annual financial statements, and therefore, these statements should be read in conjunction with the 2019 audited consolidated financial statements included within the Company’s Annual Report on Form 10-K (“Annual Report”) filed with the Securities and Exchange Commission (“SEC”) on February 28, 2020. The effects of the COVID-19 pandemic have negatively impacted the Company’s results of operations, cash flows and financial position in 2020. The Company expects these negative effects to continue, which future impacts could be material, and dependent on numerous factors that are highly uncertain, for which the ultimate impact cannot be predicted at this time, including the duration and scope of the COVID-19 pandemic. The Company’s condensed consolidated financial statements presented herein reflect the latest estimates and assumptions made by management that affect the reported amounts and related disclosures as of and for the period ended June 30, 2020. However, actual results could differ from these estimates and assumptions. The December 31, 2019 condensed consolidated balance sheet data presented herein was derived from the Company’s December 31, 2019 audited consolidated financial statements, but does not include all disclosures required by GAAP for annual periods.

Net Sales (Tables)

Net Sales (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Sales Attributed to Geographical Areas Based on Location of Sales and Long-lived Assets Attributed to Geographical Areas Based on Asset Location	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Total June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 50.9 ​ $ — ​ $ 37.4 ​ $ — ​ $ 1.3 ​ $ 89.6 ​ Europe ​ 72.3 ​ 34.9 ​ 97.8 ​ 95.1 ​ 20.6 ​ 320.7 ​ Asia-Pacific ​ 40.4 ​ 1.5 ​ 48.1 ​ 60.7 ​ 1.7 ​ ​ 152.4 ​ Rest of World ​ 1.3 ​ ​ — ​ 5.7 ​ — ​ — ​ 7.0 ​ Total ​ $ 164.9 ​ $ 36.4 ​ $ 189.0 ​ $ 155.8 ​ $ 23.6 ​ $ 569.7 ​ June 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 67.2 ​ $ — ​ $ 78.4 ​ $ — ​ $ 2.4 ​ $ 148.0 ​ Europe ​ 99.2 ​ 112.1 ​ 187.3 ​ 115.9 ​ 33.2 ​ 547.7 ​ Asia-Pacific ​ 60.8 ​ — ​ 59.7 ​ 91.2 ​ 19.3 ​ ​ 231.0 ​ Rest of World ​ 3.0 ​ ​ — ​ 22.1 ​ — ​ — ​ 25.1 ​ Total ​ $ 230.2 ​ $ 112.1 ​ $ 347.5 ​ $ 207.1 ​ $ 54.9 ​ $ 951.8 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Total June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 113.1 ​ $ — ​ $ 108.0 ​ $ — ​ $ 3.9 ​ $ 225.0 ​ Europe ​ 174.2 ​ 134.6 ​ 262.8 ​ 204.9 ​ 49.7 ​ 826.2 ​ Asia-Pacific ​ 92.8 ​ 3.4 ​ 97.9 ​ 133.7 ​ 14.8 ​ 342.6 ​ Rest of World ​ 3.9 ​ ​ — ​ 25.5 ​ — ​ — ​ 29.4 ​ Total ​ $ 384.0 ​ $ 138.0 ​ $ 494.2 ​ $ 338.6 ​ $ 68.4 ​ $ 1,423.2 ​ June 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ United States ​ $ 130.5 ​ $ — ​ $ 160.2 ​ $ — ​ $ 5.1 ​ $ 295.8 ​ Europe ​ 200.6 ​ 236.7 ​ 400.7 ​ 254.1 ​ 73.6 ​ 1,165.7 ​ Asia-Pacific ​ 117.3 ​ — ​ 111.2 ​ 181.5 ​ 43.0 ​ ​ 453.0 ​ Rest of World ​ 5.7 ​ ​ — ​ 44.7 ​ — ​ — ​ 50.4 ​ Total ​ $ 454.1 ​ $ 236.7 ​ $ 716.8 ​ $ 435.6 ​ $ 121.7 ​ $ 1,964.9 ​

Investments in Unconsolidated_2

Investments in Unconsolidated Affiliates (Tables)	6 Months Ended
	Jun. 30, 2020
Investments in Unconsolidated Affiliates
Summarized Financial Information of Unconsolidated Affiliates	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Sales $ 225.4 $ 418.4 $ 547.5 $ 787.6 ​ Gross profit ​ $ 31.3 ​ $ 85.9 ​ $ 38.4 ​ $ 140.1 ​ Net income ​ $ 20.1 ​ $ 72.8 ​ $ 11.8 ​ $ 115.7 ​

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2020
Inventories
Schedule of Inventories	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Finished goods $ 148.5 $ 210.8 Raw materials and semi-finished goods ​ 127.0 ​ 190.1 Supplies ​ 37.8 ​ 37.3 Total ​ $ 313.3 ​ $ 438.2

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt
Schedule of Debt [Table Text Block]	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ December 31, 2019 ​ ​ Interest Rate as of Maturity Date Carrying Amount Unamortized Deferred Financing Fees (1) Total Debt, Less Unamortized Deferred Financing Fees Carrying Amount Unamortized Deferred Financing Fees (1) Total Debt, Less ​ Senior Credit Facility ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2024 Term Loan B ​ 2.178% ​ September 2024 ​ $ 680.8 ​ $ (12.3) ​ $ 668.5 ​ $ 684.3 ​ $ (13.7) ​ $ 670.6 ​ 2022 Revolving Facility (2) ​ Various ​ September 2022 ​ ​ 100.0 ​ ​ — ​ ​ 100.0 ​ ​ — ​ ​ — ​ ​ — ​ 2025 Senior Notes ​ 5.375% ​ September 2025 ​ ​ 500.0 ​ ​ (6.7) ​ ​ 493.3 ​ ​ 500.0 ​ ​ (7.3) ​ ​ 492.7 ​ Accounts Receivable Securitization Facility (3) ​ Various ​ September 2021 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Other indebtedness ​ Various ​ Various ​ ​ 11.2 ​ ​ — ​ ​ 11.2 ​ ​ 10.4 ​ ​ — ​ ​ 10.4 ​ Total debt ​ ​ ​ ​ ​ $ 1,292.0 ​ $ (19.0) ​ $ 1,273.0 ​ $ 1,194.7 ​ $ (21.0) ​ $ 1,173.7 ​ Less: current portion (4) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (11.7) ​ ​ ​ ​ ​ ​ ​ ​ (11.1) ​ Total long-term debt, net of unamortized deferred financing fees ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 1,261.3 ​ ​ ​ ​ ​ ​ ​ $ 1,162.6 ​ (1) This caption does not include deferred financing fees related to the Company’s revolving facilities, which are included within “Deferred charges and other assets” on the condensed consolidated balance sheets. (2) As of June 30, 2020, under the 2022 Revolving Facility, the Company had a capacity of $375.0 million, with $100.0 million of outstanding borrowings, resulting in incremental funds available for borrowing of $261.0 million (net amount available due to $14.0 million outstanding letters of credit). Additionally, the Company is required to pay a quarterly commitment fee in respect of any unused commitments under this facility equal to 0.375% per annum. On July 24, 2020, the Company repaid the $100.0 million of outstanding borrowings on the 2022 Revolving Facility. (3) As of June 30, 2020, this facility had a borrowing capacity of $150.0 million, and the Company had approximately $110.3 million of accounts receivable available to support this facility, based on the pool of eligible accounts receivable. In regard to outstanding borrowings, fixed interest charges are 1.95% plus variable commercial paper rates, while for available, but undrawn commitments, fixed interest charges are 1.00%. (4) As of June 30, 2020 and December 31, 2019, the current portion of long-term debt primarily related to $7.0 million of the scheduled future principal payments on the 2024 Term Loan B.

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill.
Changes in Carrying Amount of Goodwill, by Segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas ​ ​ ​ ​ Binders Rubber Plastics Polystyrene Feedstocks Styrenics Total Balance at December 31, 2019 ​ $ 15.6 ​ $ 11.0 ​ $ 36.7 ​ $ 4.4 ​ $ — ​ $ — ​ $ 67.7 ​ Foreign currency impact * ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ — ​ Balance at June 30, 2020 ​ $ 15.6 ​ $ 11.0 ​ $ 36.7 ​ $ 4.4 ​ $ — ​ $ — ​ $ 67.7 ​ * For the six months ended June 30, 2020, foreign currency impact on goodwill balances totaled less than $0.1 million.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
Derivative Instruments [Abstract]
Notional Amounts of Most Significant Net Foreign Exchange Hedge Positions Outstanding	​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ Buy / (Sell) 2020 ​ Euro ​ $ (252.2) ​ Chinese Yuan ​ $ (56.1) ​ Swiss Franc ​ $ 25.7 ​ Korean Won ​ $ (14.5) ​ Mexican Peso ​ $ (12.4) ​
Schedule of Effect of Derivative Instruments on Statements of Operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Location and Amount of Gain (Loss) Recognized in ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ ​ June 30, 2020 ​ June 30, 2019 ​ ​ Cost of ​ Interest expense, net ​ Other expense, net ​ Cost of ​ Interest expense, net ​ Other expense, net Total amount of income and expense line items presented in the statements of operations in which the effects of derivative instruments are recorded ​ $ 576.8 ​ $ 11.7 ​ $ 1.0 ​ $ 865.6 ​ $ 9.9 ​ $ 1.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of cash flow hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain reclassified from AOCI into income ​ $ 0.5 ​ $ — ​ $ — ​ $ 1.6 ​ $ — ​ $ — ​ Interest rate swaps ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain (loss) reclassified from AOCI into income ​ $ — ​ $ (0.7) ​ $ — ​ $ — ​ $ 0.3 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of net investment hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain excluded from effectiveness testing ​ $ — ​ $ 2.0 ​ $ — ​ $ — ​ $ 3.9 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The effects of derivatives not designated as hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange forward contracts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of loss recognized in income ​ $ — ​ $ — ​ $ (8.1) ​ $ — ​ $ — ​ $ (2.4) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Location and Amount of Gain (Loss) Recognized in ​ ​ Six Months Ended ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ June 30, 2019 ​ ​ Cost of Interest expense, net Other expense, net Cost of Interest expense, net Other expense, net Total amount of income and expense line items presented in the statements of operations in which the effects of derivative instruments are recorded ​ $ 1,360.6 ​ $ 22.0 ​ $ 2.6 ​ $ 1,781.2 ​ $ 20.1 ​ $ 5.5 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of cash flow hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain reclassified from AOCI into income ​ $ 0.6 ​ $ — ​ $ — ​ $ 2.2 ​ $ — ​ $ — ​ Interest rate swaps ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain (loss) reclassified from AOCI into income ​ $ — ​ $ (0.7) ​ $ — ​ $ — ​ $ 0.7 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of net investment hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain excluded from effectiveness testing (1) ​ $ — ​ $ 5.4 ​ $ — ​ $ — ​ $ 7.9 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effects of derivatives not designated as hedge instruments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange forward contracts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount of gain recognized in income ​ $ — ​ $ — ​ $ 5.7 ​ $ — ​ $ — ​ $ 0.3 ​ (1) Amount for the six months ended June 30, 2020 includes the effect on AOCI from the 2017 CCS through its settlement on February 26, 2020 and the effect on AOCI from the 2020 CCS from when it was entered into on February 26, 2020 through June 30, 2020.
Schedule of Effect of Hedges on AOCI	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ` ​ Gain (Loss) Recognized in AOCI on Balance Sheet ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Designated as Cash Flow Hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges $ (1.2) $ (1.8) $ 0.9 $ 0.5 Interest rate swaps ​ ​ (0.1) ​ ​ (3.6) ​ ​ (5.9) ​ ​ (5.8) Total ​ $ (1.3) ​ $ (5.4) ​ $ (5.0) ​ $ (5.3) Designated as Net Investment Hedges ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cross currency swaps (CCS) (1) ​ $ (10.3) ​ $ (3.6) ​ $ 12.6 ​ $ 7.9 Total ​ $ (10.3) ​ $ (3.6) ​ $ 12.6 ​ $ 7.9 (1) Amount for the six months ended June 30, 2020 includes the effect on AOCI from the 2017 CCS through its settlement on February 26, 2020 and the effect on AOCI from the 2020 CCS from when it was entered into on February 26, 2020 through June 30, 2020.
Schedule of Gross and Net Unrealized Gains and Losses and Balance Sheet Classification	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Foreign ​ Foreign ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ Exchange ​ Interest ​ Cross ​ ​ ​ ​ Balance Sheet ​ Forward ​ Cash Flow ​ Rate ​ Currency ​ ​ ​ Classification Contracts ​ Hedges ​ Swaps ​ Swaps ​ Total ​ Asset Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable, net of allowance ​ $ 0.8 ​ $ 0.4 ​ $ — ​ $ 6.6 ​ $ 7.8 ​ Gross derivative asset position ​ ​ 0.8 ​ ​ 0.4 ​ ​ — ​ ​ 6.6 ​ ​ 7.8 ​ Less: Counterparty netting ​ ​ (0.6) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.6) ​ Net derivative asset position ​ $ 0.2 ​ $ 0.4 ​ $ — ​ $ 6.6 ​ $ 7.2 ​ Liability Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ (3.3) ​ $ — ​ $ (3.3) ​ $ — ​ $ (6.6) ​ Other noncurrent obligations ​ ​ — ​ ​ — ​ ​ (4.0) ​ ​ (13.5) ​ ​ (17.5) ​ Gross derivative liability position ​ ​ (3.3) ​ ​ — ​ ​ (7.3) ​ ​ (13.5) ​ ​ (24.1) ​ Less: Counterparty netting ​ ​ 0.6 ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.6 ​ Net derivative liability position ​ $ (2.7) ​ $ — ​ $ (7.3) ​ $ (13.5) ​ $ (23.5) ​ Total net derivative position ​ $ (2.5) ​ $ 0.4 ​ $ (7.3) ​ $ (6.9) ​ $ (16.3) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Foreign ​ Foreign ​ ​ ​ ​ ​ ​ ​ ​ Exchange ​ Exchange ​ Interest ​ Cross ​ ​ ​ ​ Balance Sheet ​ Forward ​ Cash Flow ​ Rate ​ Currency ​ ​ Classification Contracts Hedges Swaps Swaps Total Asset Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts receivable, net of allowance ​ $ 1.1 ​ $ — ​ $ — ​ $ 8.6 ​ $ 9.7 ​ Deferred charges and other assets ​ ​ — ​ ​ — ​ ​ — ​ ​ 19.2 ​ ​ 19.2 ​ Gross derivative asset position ​ ​ 1.1 ​ ​ — ​ ​ — ​ ​ 27.8 ​ ​ 28.9 ​ Less: Counterparty netting ​ ​ (0.4) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.4) ​ Net derivative asset position ​ $ 0.7 ​ $ — ​ $ — ​ $ 27.8 ​ $ 28.5 ​ Liability Derivatives: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts payable ​ $ (5.7) ​ $ (0.5) ​ $ (0.4) ​ $ — ​ $ (6.6) ​ Other noncurrent obligations ​ ​ — ​ ​ — ​ ​ (1.0) ​ ​ — ​ ​ (1.0) ​ Gross derivative liability position ​ ​ (5.7) ​ ​ (0.5) ​ ​ (1.4) ​ ​ — ​ ​ (7.6) ​ Less: Counterparty netting ​ ​ 0.5 ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.5 ​ Net derivative liability position ​ $ (5.2) ​ $ (0.5) ​ $ (1.4) ​ $ — ​ $ (7.1) ​ Total net derivative position ​ $ (4.5) ​ $ (0.5) ​ $ (1.4) ​ $ 27.8 ​ $ 21.4 ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Measurements
Schedule of Assets and Liabilities at Fair Value on Recurring Basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ Assets (Liabilities) at Fair Value (Level 1) (Level 2) (Level 3) Total Foreign exchange forward contracts—Assets $ — $ 0.2 $ — $ 0.2 ​ Foreign exchange forward contracts—(Liabilities) ​ — ​ (2.7) ​ — ​ (2.7) ​ Foreign exchange cash flow hedges—Assets ​ ​ — ​ ​ 0.4 ​ ​ — ​ ​ 0.4 ​ Interest rate swaps—(Liabilities) ​ ​ — ​ ​ (7.3) ​ ​ — ​ ​ (7.3) ​ Cross currency swaps—Assets ​ ​ — ​ ​ 6.6 ​ ​ — ​ ​ 6.6 ​ Cross currency swaps—(Liabilities) ​ ​ — ​ ​ (13.5) ​ ​ — ​ ​ (13.5) ​ Total fair value ​ $ — ​ $ (16.3) ​ $ — ​ $ (16.3) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ Assets (Liabilities) at Fair Value (Level 1) (Level 2) (Level 3) Total Foreign exchange forward contracts—Assets ​ $ — $ 0.7 $ — $ 0.7 ​ Foreign exchange forward contracts—(Liabilities) ​ ​ — ​ ​ (5.2) ​ ​ — ​ ​ (5.2) ​ Foreign exchange cash flow hedges—(Liabilities) ​ ​ — ​ ​ (0.5) ​ ​ — ​ ​ (0.5) ​ Interest rate swaps—(Liabilities) ​ ​ — ​ ​ (1.4) ​ ​ — ​ ​ (1.4) ​ Cross currency swaps—Assets ​ ​ — ​ ​ 27.8 ​ ​ — ​ ​ 27.8 ​ Total fair value ​ $ — ​ $ 21.4 ​ $ — ​ $ 21.4 ​
Schedule of Assets and Liabilities at Fair Value on Nonrecurring Basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ ​ Quoted Prices in Active Markets for Identical Items ​ Significant Other Observable Inputs ​ Significant Unobservable Inputs ​ ​ ​ ​ ​ (Level 1) (Level 2) (Level 3) Total ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Boehlen styrene monomer property, plant and equipment ​ $ — ​ $ — ​ $ 3.3 ​ $ 3.3 ​ Schkopau PBR property, plant and equipment ​ ​ — ​ ​ — ​ ​ 1.5 ​ ​ 1.5 ​ Total fair value ​ $ — ​ $ — ​ $ 4.8 ​ $ 4.8 ​
Estimated Fair Value of Outstanding Debt Not Carried at Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ June 30, 2020 December 31, 2019 2025 Senior Notes ​ $ 476.1 ​ $ 503.7 ​ 2024 Term Loan B ​ ​ 650.2 ​ ​ 686.4 ​ Total fair value ​ $ 1,126.3 ​ $ 1,190.1 ​

Provision for Income Taxes (Tab

Provision for Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2020
Provision for Income Taxes
Schedule of Effective Tax Rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 2019 2020 2019 ​ Effective income tax rate ​ ​ (101.5) % ​ 36.0 % ​ (47.2) % ​ 29.3 % ​

Pension Plans and Other Postr_2

Pension Plans and Other Postretirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2020
Pension Plans and Other Postretirement Benefits
Schedule of Net Periodic Benefit Costs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Defined Benefit Pension Plans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Service cost ​ $ 4.2 ​ $ 3.1 $ 8.6 ​ $ 6.3 ​ Interest cost ​ 0.8 ​ 1.2 ​ 1.6 ​ 2.5 ​ Expected return on plan assets ​ (0.3) ​ (0.5) ​ (0.6) ​ (1.0) ​ Amortization of prior service credit ​ (0.3) ​ (0.3) ​ (0.6) ​ (0.5) ​ Amortization of net loss ​ 1.2 ​ 0.8 ​ 2.3 ​ 1.5 ​ Net settlement loss ​ — ​ — ​ — ​ 0.7 ​ Net periodic benefit cost ​ $ 5.6 ​ $ 4.3 ​ $ 11.3 ​ $ 9.5 ​

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Share-Based Compensation Expense and Unrecognized Compensation Cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ ​ ​ Three Months Ended ​ Six Months Ended June 30, 2020 ​ ​ ​ June 30, ​ June 30, Unrecognized ​ Weighted ​ ​ 2020 2019 2020 2019 Compensation Cost Average Years ​ RSUs ​ $ 1.8 ​ $ 1.9 ​ $ 3.5 ​ $ 4.0 $ 12.3 ​ 2.0 ​ Options ​ ​ 0.8 ​ ​ 0.8 ​ ​ 1.8 ​ ​ 2.0 ​ 2.7 ​ 1.4 ​ PSUs ​ ​ 0.5 ​ ​ 0.8 ​ ​ 1.0 ​ ​ 1.7 ​ 3.7 ​ 2.1 ​ Total share-based compensation expense ​ $ 3.1 ​ $ 3.5 ​ $ 6.3 ​ $ 7.7 ​ ​ ​ ​ ​
Summary of Awards Granted and Weighted Average Grant-Date Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ ​ ​ Awards Granted ​ Weighted Average Grant Date Fair Value per Award ​ RSUs ​ ​ 355,818 ​ $ 24.13 ​ Options ​ ​ 530,241 ​ ​ 6.51 ​ PSUs ​ ​ 102,545 ​ ​ 24.54 ​
Option Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Weighted-average Assumptions	​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, 2020 ​ Expected term (in years) 5.50 ​ Expected volatility 39.93 % Risk-free interest rate 1.19 % Dividend yield ​ 3.25 %
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Weighted-average Assumptions	​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ ​ June 30, 2020 ​ Expected term (in years) ​ 3.00 ​ Expected volatility 40.50 % Risk-free interest rate 1.16 % Share price $ 24.30 ​

Segments (Tables)

Segments (Tables)	6 Months Ended
	Jun. 30, 2020
Segments
Schedule of Segment Reporting Information, by Segment [Table Text Block]	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas Three Months Ended (1) ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Styrenics June 30, 2020 $ 17.0 $ (27.7) $ (5.6) ​ $ 14.8 $ (3.5) $ 14.4 ​ June 30, 2019 ​ $ 20.6 ​ $ 12.9 ​ $ 34.2 ​ $ 16.2 ​ $ (0.6) ​ $ 40.3 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Latex ​ Synthetic ​ Performance ​ ​ ​ ​ ​ Americas Six Months Ended (1) ​ Binders ​ Rubber ​ Plastics ​ Polystyrene ​ Feedstocks ​ Styrenics June 30, 2020 $ 38.6 ​ $ (12.5) ​ $ 31.2 ​ $ 26.6 ​ $ (19.8) ​ $ 24.2 ​ June 30, 2019 ​ $ 38.1 ​ $ 21.7 ​ $ 69.9 ​ $ 32.9 ​ $ 16.6 ​ $ 72.5 ​ (1) The Company’s primary measure of segment operating performance is Adjusted EBITDA, which is defined as income from continuing operations before interest expense, net; provision for income taxes; depreciation and amortization expense; loss on extinguishment of long-term debt; asset impairment charges; gains or losses on the dispositions of businesses and assets; restructuring charges; acquisition related costs and benefits and other items. Segment Adjusted EBITDA is a key metric that is used by management to evaluate business performance in comparison to budgets, forecasts, and prior year financial results, providing a measure that management believes reflects core operating performance by removing the impact of transactions and events that would not be considered a part of core operations. Other companies in the industry may define segment Adjusted EBITDA differently than the Company, and as a result, it may be difficult to use segment Adjusted EBITDA, or similarly named financial measures, that other companies may use to compare the performance of those companies to the Company’s segment performance. ​
Reconciliation of IBT to Adjusted EBITDA	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 Income (loss) before income taxes ​ $ (63.7) ​ $ 43.7 ​ $ (111.9) ​ $ 90.3 ​ Interest expense, net ​ 11.7 ​ 9.9 ​ 22.0 ​ 20.1 ​ Depreciation and amortization ​ 34.8 ​ 34.7 ​ ​ 71.1 ​ 68.7 ​ Corporate Unallocated (2) ​ ​ 17.7 ​ ​ 20.8 ​ ​ 39.6 ​ ​ 46.9 ​ Adjusted EBITDA Addbacks (3) ​ 8.9 ​ 14.5 ​ 67.5 ​ 25.7 ​ Segment Adjusted EBITDA ​ $ 9.4 ​ $ 123.6 ​ $ 88.3 ​ $ 251.7 ​ (2) Corporate unallocated includes corporate overhead costs and certain other income and expenses. (3) Adjusted EBITDA addbacks for the three and six months ended June 30, 2020 and 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 2019 2020 2019 Net gain on disposition of businesses and assets ​ $ — ​ $ — ​ $ (0.4) ​ $ (0.2) ​ Restructuring and other charges (Note 16) ​ ​ 6.3 ​ ​ (0.3) ​ ​ 8.1 ​ ​ 0.1 ​ Acquisition transaction and integration net costs ​ ​ (0.4) ​ ​ 0.7 ​ ​ (0.3) ​ ​ 0.7 ​ Asset impairment charges or write-offs (Note 9) ​ ​ — ​ ​ — ​ ​ 38.3 ​ ​ — ​ Other items (a) ​ ​ 3.0 ​ ​ 14.1 ​ ​ 21.8 ​ ​ 25.1 ​ Total Adjusted EBITDA Addbacks ​ $ 8.9 ​ $ 14.5 ​ $ 67.5 ​ $ 25.7 ​ (a) Other items for the three and six months ended June 30, 2020 and 2019 primarily relate to advisory and professional fees incurred in conjunction with the Company’s initiative to transition business services from Dow, including certain administrative services such as accounts payable, logistics, finance, and IT services. Also included within other items for the three and six months ended June 30, 2020 and 2019 are fees incurred in conjunction with certain of the Company’s strategic initiatives.

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2020
Restructuring
Detail of Restructuring Charges	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ Cumulative ​ ​ ​ ​ ​ June 30, ​ June 30, ​ Life-to-date ​ ​ ​ ​ ​ 2020 2019 ​ 2020 2019 ​ Charges Segment ​ Corporate Restructuring Program ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accelerated depreciation ​ $ 1.2 ​ $ — ​ $ 2.5 ​ $ — ​ $ 2.9 ​ ​ ​ Employee termination benefits ​ ​ 4.1 ​ ​ — ​ ​ 4.4 ​ ​ — ​ ​ 21.4 ​ ​ ​ Contract terminations ​ ​ 1.2 ​ ​ — ​ ​ 2.4 ​ ​ — ​ ​ 2.8 ​ ​ ​ Corporate Program Subtotal ​ $ 6.5 ​ $ — ​ $ 9.3 ​ $ — ​ $ 27.1 ​ N/A (1) ​ Terneuzen Compounding Restructuring ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset impairment/accelerated depreciation ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 3.1 ​ ​ ​ Employee termination benefits ​ ​ — ​ ​ (0.4) ​ ​ — ​ ​ (0.4) ​ ​ 0.7 ​ ​ ​ Contract terminations ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.3 ​ ​ ​ Decommissioning and other ​ ​ 0.1 ​ ​ — ​ ​ 0.2 ​ ​ 0.2 ​ ​ 2.2 ​ ​ ​ Terneuzen Subtotal ​ $ 0.1 ​ $ (0.4) ​ $ 0.2 ​ $ (0.2) ​ $ 6.3 ​ Performance Plastics (2) ​ Livorno Plant Restructuring ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset impairment/accelerated depreciation ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 14.7 ​ ​ ​ Employee termination benefits ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 5.4 ​ ​ ​ Contract terminations ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.3 ​ ​ ​ Decommissioning and other ​ ​ — ​ ​ 0.1 ​ ​ 0.2 ​ ​ 0.3 ​ ​ 4.4 ​ ​ ​ Livorno Subtotal ​ $ — ​ $ 0.1 ​ $ 0.2 ​ $ 0.3 ​ $ 24.8 ​ Latex Binders (3) ​ Other Restructurings ​ ​ 0.9 ​ ​ — ​ ​ 0.9 ​ ​ — ​ ​ ​ ​ Various ​ Total Restructuring Charges ​ $ 7.5 ​ $ (0.3) ​ $ 10.6 ​ $ 0.1 ​ ​ ​ ​ ​ ​ (1) In November 2019, the Company announced a corporate restructuring program associated with the Company’s shift to a global functional structure and business excellence initiatives to drive greater focus on business process optimization and efficiency, which continued through the six months ended June 30, 2020. In connection with this restructuring plan, the Company incurred employee termination benefit charges of $4.1 million, inclusive of a share-based compensation benefit of $1.4 million, contract termination charges of $1.2 million, and accelerated depreciation charges of $1.2 million during the three months ended June 30, 2020. Employee termination benefit charges of $4.4 million, contract termination charges of $2.4 million, and accelerated depreciation charges of $2.5 million were incurred during the six months ended June 30, 2020. The Company expects to incur incremental employee termination benefit charges of less than $1.0 million, inclusive of pension charges, through the end of 2020, and the majority of these total benefits are expected to be paid by the end of 2020. As this was identified as a corporate-related activity, the charges related to this restructuring program were not allocated to a specific segment, but rather included within corporate unallocated. (2) In 2017, the Company announced plans to upgrade its production capability for compounded resins with the construction of a new state-of-the art compounding facility to replace its existing compounding facility in Terneuzen, The Netherlands. As of June 30, 2020, the new facility is complete, along with all substantive transition and quality assurance activities. Production at the prior facility ceased and decommissioning activities began in 2019, and are expected to continue through the first half of 2021. The Company estimates it will incur incremental decommissioning and other charges of less than $1.0 million through 2021, the majority of which are expected to be paid during the remainder of 2020. (3) In 2016, the Company ceased manufacturing activities at its latex binders manufacturing facility in Livorno, Italy and began decommissioning activities. In 2018, the Company entered into an agreement to sell the land where the former facility is located. This land sale closed in January 2020, for a total purchase price of $12.5 million. A prepayment of $1.3 million of this purchase price was received in 2018, and was recorded within “Accrued expenses and other current liabilities” on the condensed consolidated balance sheets as of December 31, 2019. The remaining purchase price was received in January 2020 when the transaction closed. The Company recorded a net gain on sale of $0.6 million during the six months ended June 30, 2020, which was recorded within “Selling, general and administrative expenses” in the condensed consolidated statements of operations.
Rollforward of Liability Balances	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Balance at ​ December 31, 2019 Expenses Deductions (1) June 30, 2020 Employee termination benefits ​ $ 17.2 ​ $ 6.7 ​ $ (7.0) ​ $ 16.9 ​ Contract terminations ​ ​ 0.7 ​ ​ — ​ ​ (0.5) ​ ​ 0.2 ​ Decommissioning and other ​ — ​ 0.4 ​ (0.4) ​ — ​ Total ​ $ 17.9 ​ $ 7.1 ​ $ (7.9) ​ $ 17.1 ​ (1) Primarily includes payments made against the existing accrual, as well as immaterial impacts of foreign currency remeasurement.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2020
Shareholders' Equity.
Components of AOCI, Net of Income Taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative Pension & Other ​ ​ ​ ​ ​ ​ ​ ​ Translation ​ Postretirement Benefit ​ ​ Cash Flow ​ ​ ​ ​ Three Months Ended June 30, 2020 and 2019 Adjustments Plans, Net ​ Hedges, Net Total Balance as of March 31, 2020 ​ $ (96.0) ​ $ (55.1) ​ $ (3.1) ​ $ (154.2) ​ Other comprehensive loss ​ (1.1) ​ — ​ (1.5) ​ (2.6) ​ Amounts reclassified from AOCI to net income (1) ​ ​ — ​ ​ 0.5 ​ ​ 0.2 ​ ​ 0.7 ​ Balance as of June 30, 2020 ​ $ (97.1) ​ $ (54.6) ​ $ (4.4) ​ $ (156.1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of March 31, 2019 ​ $ (112.1) ​ $ (40.4) ​ $ 9.0 ​ $ (143.5) ​ Other comprehensive income (loss) ​ 3.0 ​ — ​ (3.5) ​ (0.5) ​ Amounts reclassified from AOCI to net income (loss) (1) ​ ​ — ​ ​ 0.3 ​ ​ (1.9) ​ ​ (1.6) ​ Balance as of June 30, 2019 ​ $ (109.1) ​ $ (40.1) ​ $ 3.6 ​ $ (145.6) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cumulative Pension & Other ​ ​ ​ ​ ​ ​ ​ Translation ​ Postretirement Benefit ​ Cash Flow ​ ​ ​ ​ Six Months Ended June 30, 2020 and 2019 ​ Adjustments Plans, Net Hedges, Net Total ​ Balance as of December 31, 2019 ​ $ (106.7) ​ $ (56.3) ​ $ 0.6 ​ $ (162.4) ​ Other comprehensive income (loss) ​ 9.6 ​ 0.6 ​ (5.1) ​ 5.1 ​ Amounts reclassified from AOCI to net income (1) ​ ​ — ​ ​ 1.1 ​ ​ 0.1 ​ ​ 1.2 ​ Balance as of June 30, 2020 ​ $ (97.1) ​ $ (54.6) ​ $ (4.4) ​ $ (156.1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance as of December 31, 2018 ​ $ (111.8) ​ $ (39.4) ​ $ 8.9 ​ $ (142.3) ​ Other comprehensive income (loss) ​ 2.7 ​ (2.0) ​ (2.4) ​ (1.7) ​ Amounts reclassified from AOCI to net income (loss) (1) ​ ​ — ​ ​ 1.3 ​ ​ (2.9) ​ ​ (1.6) ​ Balance as of June 30, 2019 ​ $ (109.1) ​ $ (40.1) ​ $ 3.6 ​ $ (145.6) ​
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ AOCI Components ​ June 30, ​ June 30, ​ Statements of Operations ​ ​ 2020 2019 2020 2019 Classification ​ Cash flow hedging items ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign exchange cash flow hedges ​ $ (0.5) ​ $ (1.6) ​ $ (0.6) ​ $ (2.2) ​ Cost of sales ​ Interest rate swaps ​ ​ 0.7 ​ ​ (0.3) ​ ​ 0.7 ​ ​ (0.7) ​ Interest expense, net ​ Total before tax ​ ​ 0.2 ​ ​ (1.9) ​ ​ 0.1 ​ ​ (2.9) ​ ​ ​ Tax effect ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Provision for income taxes ​ Total, net of tax ​ $ 0.2 ​ $ (1.9) ​ $ 0.1 ​ $ (2.9) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of pension and other postretirement benefit plan items ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prior service credit ​ $ (0.3) ​ $ (0.3) ​ $ (0.6) ​ $ (0.6) ​ (a) ​ Net actuarial loss ​ ​ 1.1 ​ ​ 0.8 ​ ​ 2.3 ​ ​ 1.6 ​ (a) ​ Net settlement loss ​ ​ — ​ ​ — ​ ​ — ​ ​ 0.7 ​ (a) ​ Total before tax ​ ​ 0.8 ​ ​ 0.5 ​ ​ 1.7 ​ ​ 1.7 ​ ​ ​ Tax effect ​ ​ (0.3) ​ ​ (0.2) ​ ​ (0.6) ​ ​ (0.4) ​ Provision for income taxes ​ Total, net of tax ​ $ 0.5 ​ $ 0.3 ​ $ 1.1 ​ $ 1.3 ​ ​ ​ (a) These AOCI components are included in the computation of net periodic benefit costs (see Note 12).

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share
Schedule of Earnings per Share Basic and Diluted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (in millions, except per share data) 2020 2019 2020 2019 Earnings: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (128.4) ​ $ 28.0 ​ $ (164.7) ​ $ 63.8 ​ Shares: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average ordinary shares outstanding ​ 38.2 ​ 40.8 ​ 38.4 ​ 41.0 ​ Dilutive effect of RSUs, option awards, and PSUs (1) ​ — ​ 0.3 ​ — ​ 0.5 ​ Diluted weighted average ordinary shares outstanding ​ 38.2 ​ 41.1 ​ 38.4 ​ 41.5 ​ Income (loss) per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income (loss) per share—basic ​ $ (3.36) ​ $ 0.69 ​ $ (4.29) ​ $ 1.56 ​ Income (loss) per share—diluted ​ $ (3.36) ​ $ 0.68 ​ $ (4.29) ​ $ 1.54 ​ (1) Refer to Note 13 for discussion of RSUs, option awards, and PSUs granted to certain Company directors and employees. As the Company recorded a net loss for the three and six months ended June 30, 2020, potential shares related to equity-based awards have been excluded from the calculation of diluted EPS, as doing so would be anti-dilutive. The number of anti-dilutive shares that have been excluded from the computation of diluted earnings per share were 0.7 million and 0.8 million for the three and six months ended June 30, 2019, respectively.

Net Sales (Details)

Net Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 569.7	$ 951.8	$ 1,423.2	$ 1,964.9
Latex Binders Segment
Disaggregation of Revenue [Line Items]
Net sales	164.9	230.2	384	454.1
Synthetic Rubber Segment
Disaggregation of Revenue [Line Items]
Net sales	36.4	112.1	138	236.7
Performance Plastics Segment [Member]
Disaggregation of Revenue [Line Items]
Net sales	189	347.5	494.2	716.8
Polystyrene [Member]
Disaggregation of Revenue [Line Items]
Net sales	155.8	207.1	338.6	435.6
Feedstocks [Member]
Disaggregation of Revenue [Line Items]
Net sales	23.6	54.9	68.4	121.7
United States [Member]
Disaggregation of Revenue [Line Items]
Net sales	89.6	148	225	295.8
United States [Member] | Latex Binders Segment
Disaggregation of Revenue [Line Items]
Net sales	50.9	67.2	113.1	130.5
United States [Member] | Performance Plastics Segment [Member]
Disaggregation of Revenue [Line Items]
Net sales	37.4	78.4	108	160.2
United States [Member] | Feedstocks [Member]
Disaggregation of Revenue [Line Items]
Net sales	1.3	2.4	3.9	5.1
Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	320.7	547.7	826.2	1,165.7
Europe [Member] | Latex Binders Segment
Disaggregation of Revenue [Line Items]
Net sales	72.3	99.2	174.2	200.6
Europe [Member] | Synthetic Rubber Segment
Disaggregation of Revenue [Line Items]
Net sales	34.9	112.1	134.6	236.7
Europe [Member] | Performance Plastics Segment [Member]
Disaggregation of Revenue [Line Items]
Net sales	97.8	187.3	262.8	400.7
Europe [Member] | Polystyrene [Member]
Disaggregation of Revenue [Line Items]
Net sales	95.1	115.9	204.9	254.1
Europe [Member] | Feedstocks [Member]
Disaggregation of Revenue [Line Items]
Net sales	20.6	33.2	49.7	73.6
Asia-Pacific [Member]
Disaggregation of Revenue [Line Items]
Net sales	152.4	231	342.6	453
Asia-Pacific [Member] | Latex Binders Segment
Disaggregation of Revenue [Line Items]
Net sales	40.4	60.8	92.8	117.3
Asia-Pacific [Member] | Synthetic Rubber Segment
Disaggregation of Revenue [Line Items]
Net sales	1.5		3.4
Asia-Pacific [Member] | Performance Plastics Segment [Member]
Disaggregation of Revenue [Line Items]
Net sales	48.1	59.7	97.9	111.2
Asia-Pacific [Member] | Polystyrene [Member]
Disaggregation of Revenue [Line Items]
Net sales	60.7	91.2	133.7	181.5
Asia-Pacific [Member] | Feedstocks [Member]
Disaggregation of Revenue [Line Items]
Net sales	1.7	19.3	14.8	43
Rest of World [Member]
Disaggregation of Revenue [Line Items]
Net sales	7	25.1	29.4	50.4
Rest of World [Member] | Latex Binders Segment
Disaggregation of Revenue [Line Items]
Net sales	1.3	3	3.9	5.7
Rest of World [Member] | Performance Plastics Segment [Member]
Disaggregation of Revenue [Line Items]
Net sales	$ 5.7	$ 22.1	$ 25.5	$ 44.7

Investments in Unconsolidated_3

Investments in Unconsolidated Affiliates - Summarized Financial Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)item	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)item	Jun. 30, 2019USD ($)
Investments in Unconsolidated Affiliates - Summarized Information
Number of joint ventures | item	1		1
Summarized Financial Information, Net Income
Sales	$ 225.4	$ 418.4	$ 547.5	$ 787.6
Gross profit	31.3	85.9	38.4	140.1
Net income	$ 20.1	$ 72.8	$ 11.8	$ 115.7

Investments in Unconsolidated_4

Investments in Unconsolidated Affiliates - Detail (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Investments in Unconsolidated Affiliates
Investments in unconsolidated affiliates		$ 212.3		$ 188.1
Americas Styrenics
Investments in Unconsolidated Affiliates
Investments in unconsolidated affiliates		212.3		188.1
Investment in unconsolidated affiliates-difference between carrying amount and underlying equity		$ 7.8		$ (10.3)
Percentage of ownership underlying net assets		50.00%		50.00%
Amortized weighted average remaining useful life		1.9
Dividends received from operating activities	$ 40		$ 52.5

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Inventories
Finished goods	$ 148.5	$ 210.8
Raw materials and semi-finished goods	127	190.1
Supplies	37.8	37.3
Total	$ 313.3	$ 438.2

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Jul. 24, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Feb. 26, 2020	Dec. 31, 2019	Sep. 01, 2017
Debt Instruments
Carrying amount		$ 1,292		$ 1,292			$ 1,194.7
Unamortized deferred financing fees		(19)		(19)			(21)
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		1,273		1,273			1,173.7
Less: current portion		(11.7)		(11.7)			(11.1)
Total long-term debt, net of unamortized deferred financing fees		1,261.3		1,261.3			1,162.6
Interest and Debt Expense [Abstract]
Interest expense, net		$ 11.7	$ 9.9	$ 22	$ 20.1
2024 Term Loan B
Debt Instruments
Interest rate at end of period (as a percent)		2.178%		2.178%
Carrying amount		$ 680.8		$ 680.8			684.3
Unamortized deferred financing fees		(12.3)		(12.3)			(13.7)
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		668.5		668.5			670.6
Less: current portion		(7)		$ (7)			(7)
2024 Term Loan B | LIBOR [Member]
Debt Instruments
Debt instrument, margin rate				2.00%
2022 Revolving Facility
Debt Instruments
Carrying amount		100		$ 100
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		100		100
Funds available for borrowings		261		261
Letters of credit, amount outstanding		14		$ 14
Commitment fee (as a percent)				0.375%
Maximum borrowing capacity		$ 375		$ 375
2022 Revolving Facility | Subsequent Event [Member]
Debt Instruments
Repayments on the revolving debt	$ 100
2025 Senior Notes
Debt Instruments
Interest rate		5.375%		5.375%		5.375%		5.375%
Carrying amount		$ 500		$ 500			500
Unamortized deferred financing fees		(6.7)		(6.7)			(7.3)
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		493.3		493.3			492.7
Accounts Receivable Securitization Facility [Member]
Debt Instruments
Carrying amount		0		0			0
Unamortized deferred financing fees		0		0			0
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		0		$ 0			0
Commitment fee (as a percent)				1.00%
Maximum borrowing capacity		150		$ 150
Accounts receivable available to support facility		$ 110.3		$ 110.3
Accounts Receivable Securitization Facility [Member] | Base Rate [Member]
Debt Instruments
Interest rate		1.95%		1.95%
Other Indebtedness [Member]
Debt Instruments
Carrying amount		$ 11.2		$ 11.2			10.4
Total Debt, Less Unamortized Deferred Financing Fees, Current and Noncurrent		$ 11.2		$ 11.2			$ 10.4

Goodwill (Details)

Goodwill (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 67.7
Ending Balance	67.7
Maximum
Goodwill [Roll Forward]
Foreign currency impact	$ 0.1

Derivative Instruments (Details

Derivative Instruments (Details) € in Millions	Feb. 26, 2020USD ($)	Sep. 01, 2017USD ($)	Jun. 30, 2020USD ($)item	Feb. 26, 2020EUR (€)	Dec. 31, 2019USD ($)	Apr. 01, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 01, 2017EUR (€)
Derivative Instruments
Total debt			$ 1,273,000,000		$ 1,173,700,000
Cumulative foreign currency translation loss			$ 0
Foreign Exchange Forward Contracts
Derivative Instruments
Derivative term			2 months
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			$ 390,900,000
Foreign Exchange Forward Contracts | Designated as Hedging Instrument
Derivative Instruments
Derivative contracts, notional amount			$ 42,000,000
Derivative term			6 months
Number of subsidiaries participating | item			1
Cross Currency Swap | Net Investment Hedges
Derivative Instruments
Derivative contracts, notional amount | €								€ 420
Derivative term	2 years 8 months 12 days	5 years
Cross currency swap weighted average interest rate (as a percent)	3.672%	3.45%
Amount hedged	$ 500,000,000	$ 500,000,000		€ 459.3
Cumulative translation adjustment, net of tax							$ 38,000,000
Initial excluded component value	13,800,000					$ 23,600,000
Cash proceeds	$ 51,600,000
Interest Rate Swap
Derivative Instruments
Derivative contracts, notional amount			$ 200,000,000
Fixed interest rate per agreement (as a percent)			1.81%
LIBOR rate at end of period (as a percent)			0.18%
2025 Senior Notes
Derivative Instruments
Total debt			$ 493,300,000		492,700,000
Interest rate	5.375%	5.375%	5.375%	5.375%				5.375%
2024 Term Loan B
Derivative Instruments
Total debt			$ 668,500,000		$ 670,600,000
2024 Term Loan B | LIBOR [Member]
Derivative Instruments
Debt instrument, margin rate			2.00%
Variable rate floor (as a percent)			0.00%
Euro [Member] | Foreign Exchange Forward Contracts | Sell | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			$ 252,200,000
Chinese Yuan [Member] | Foreign Exchange Forward Contracts | Sell | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			56,100,000
Swiss Franc [Member] | Foreign Exchange Forward Contracts | Buy | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			25,700,000
Korea (South), Won | Foreign Exchange Forward Contracts | Sell | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			14,500,000
Mexico, Pesos | Foreign Exchange Forward Contracts | Sell | Not Designated as Hedging Instruments - Economic
Derivative Instruments
Derivative contracts, notional amount			$ 12,400,000

Derivative Instruments - Income

Derivative Instruments - Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Cost of sales	$ 576.8	$ 865.6	$ 1,360.6	$ 1,781.2
Interest expense, net	11.7	9.9	22	20.1
Other expense, net	1	1.5	2.6	5.5
Cost of Sales
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Cost of sales	576.8		1,360.6	1,781.2
Interest Expense, Net
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Interest expense, net	11.7	9.9	22	20.1
Other Expense, Net
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Other expense, net	1	1.5	2.6	5.5
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic | Other Expense, Net
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Amount of gain recognized in income, not designated	(8.1)	(2.4)	5.7	0.3
Foreign Exchange Forward Contracts | Designated as Hedging Instrument
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Amount of gain (loss) reclassified from AOCI into income, foreign exchange cash flow hedges		1.6
Foreign Exchange Forward Contracts | Designated as Hedging Instrument | Cost of Sales
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Amount of gain (loss) reclassified from AOCI into income, foreign exchange cash flow hedges	0.5		0.6	2.2
Cross Currency Swap | Interest Expense, Net
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Amount of gain excluded from effectiveness testing	2	3.9	5.4	7.9
Interest Rate Swap | Interest Expense, Net
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Amount of gain (loss) reclassified from AOCI into income, interest rate cash flow hedges	$ (0.7)	$ 0.3	$ (0.7)	$ 0.7

Derivative Instruments - Effect

Derivative Instruments - Effect on AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments
Gain (Loss) Recognized in AOCI, Cash flow hedges	$ (1.3)	$ (5.4)	$ (5)	$ (5.3)
Gain (Loss) Recognized in AOCI, Net investment hedges	(10.3)	(3.6)	12.6	7.9
Foreign Exchange Forward Contracts
Derivative Instruments
Gain (Loss) Recognized in AOCI, Cash flow hedges	(1.2)	(1.8)	0.9	0.5
Cross Currency Swap
Derivative Instruments
Gain (Loss) Recognized in AOCI, Net investment hedges	(10.3)	(3.6)	12.6	7.9
Interest Rate Swap
Derivative Instruments
Gain (Loss) Recognized in AOCI, Cash flow hedges	$ (0.1)	$ (3.6)	$ (5.9)	$ (5.8)

Derivative Instruments - Gains

Derivative Instruments - Gains and Losses text (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Foreign exchange transaction gains (losses)	$ 8,700,000	$ 2,600,000	$ (5,300,000)	$ (500,000)
Information regarding changes in fair value of derivatives
Current foreign currency translation gain			0
Maximum
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Reclassification expected during next 12 months			(2,900,000)
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic
Derivative, Gain (Loss) on Derivative, Net [Abstract]
Gain (loss) from settlements and changes in fair value	$ (8,100,000)	$ (2,400,000)	$ 5,700,000	$ 300,000

Derivative Instruments - Financ

Derivative Instruments - Financial Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	$ 7.8	$ 28.9
Counterparty netting, derivative assets	(0.6)	(0.4)
Net derivative asset position	7.2	28.5
Gross derivative liability position	(24.1)	(7.6)
Counterparty netting, derivative liabilities	0.6	0.5
Net derivative liability position	(23.5)	(7.1)
Total net derivative position	(16.3)	21.4
Accounts Receivable
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	7.8	9.7
Deferred Charges and Other Assets
Derivatives, Financial Assets and Liabilities
Gross derivative asset position		19.2
Accounts Payable
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(6.6)	(6.6)
Other Noncurrent Obligations
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(17.5)	(1)
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	0.8	1.1
Counterparty netting, derivative assets	(0.6)	(0.4)
Net derivative asset position	0.2	0.7
Gross derivative liability position	(3.3)	(5.7)
Counterparty netting, derivative liabilities	0.6	0.5
Net derivative liability position	(2.7)	(5.2)
Total net derivative position	(2.5)	(4.5)
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic | Accounts Receivable
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	0.8	1.1
Foreign Exchange Forward Contracts | Not Designated as Hedging Instruments - Economic | Accounts Payable
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(3.3)	(5.7)
Foreign Exchange Forward Contracts | Designated as Hedging Instrument
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	0.4
Net derivative asset position	0.4
Gross derivative liability position		(0.5)
Net derivative liability position		(0.5)
Total net derivative position	0.4	(0.5)
Foreign Exchange Forward Contracts | Designated as Hedging Instrument | Accounts Receivable
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	0.4
Foreign Exchange Forward Contracts | Designated as Hedging Instrument | Accounts Payable
Derivatives, Financial Assets and Liabilities
Gross derivative liability position		(0.5)
Interest Rate Swap
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(7.3)	(1.4)
Net derivative liability position	(7.3)	(1.4)
Total net derivative position	(7.3)	(1.4)
Interest Rate Swap | Accounts Payable
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(3.3)	(0.4)
Interest Rate Swap | Other Noncurrent Obligations
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	(4)	(1)
Cross Currency Swap
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	6.6	27.8
Net derivative asset position	6.6	27.8
Gross derivative liability position	(13.5)
Net derivative liability position	(13.5)
Total net derivative position	(6.9)	27.8
Cross Currency Swap | Accounts Receivable
Derivatives, Financial Assets and Liabilities
Gross derivative asset position	6.6	8.6
Cross Currency Swap | Deferred Charges and Other Assets
Derivatives, Financial Assets and Liabilities
Gross derivative asset position		$ 19.2
Cross Currency Swap | Other Noncurrent Obligations
Derivatives, Financial Assets and Liabilities
Gross derivative liability position	$ (13.5)

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value, Recurring (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Fair Value Measurements
Total net derivative position	$ (16.3)	$ 21.4
Property, plant and equipment, net	573.5	625.8
Boehlen Location [Member]
Fair Value Measurements
Property, plant and equipment, net	3.3
Impairment loss on assets	10.3
Schkopau PBR Location [Member]
Fair Value Measurements
Property, plant and equipment, net	1.5
Impairment loss on assets	28
Interest Rate Swap
Fair Value Measurements
Total net derivative position	(7.3)	(1.4)
Cross Currency Swap
Fair Value Measurements
Total net derivative position	(6.9)	27.8
Designated as Hedging Instrument | Foreign Exchange Forward Contracts
Fair Value Measurements
Total net derivative position	0.4	(0.5)
Not Designated as Hedging Instruments - Economic | Foreign Exchange Forward Contracts
Fair Value Measurements
Total net derivative position	(2.5)	(4.5)
Recurring
Fair Value Measurements
Total net derivative position	(16.3)	21.4
Recurring | Interest Rate Swap
Fair Value Measurements
Liabilities at fair value	(7.3)	(1.4)
Recurring | Cross Currency Swap
Fair Value Measurements
Assets at fair value	6.6	27.8
Liabilities at fair value	(13.5)
Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Measurements
Total net derivative position	(16.3)	21.4
Recurring | Significant Other Observable Inputs (Level 2) | Interest Rate Swap
Fair Value Measurements
Liabilities at fair value	(7.3)	(1.4)
Recurring | Significant Other Observable Inputs (Level 2) | Cross Currency Swap
Fair Value Measurements
Assets at fair value	6.6	27.8
Liabilities at fair value	(13.5)
Recurring | Designated as Hedging Instrument | Foreign Exchange Forward Contracts
Fair Value Measurements
Assets at fair value	0.4
Liabilities at fair value		(0.5)
Recurring | Designated as Hedging Instrument | Significant Other Observable Inputs (Level 2) | Foreign Exchange Forward Contracts
Fair Value Measurements
Assets at fair value	0.4
Liabilities at fair value		(0.5)
Recurring | Not Designated as Hedging Instruments - Economic | Foreign Exchange Forward Contracts
Fair Value Measurements
Assets at fair value	0.2	0.7
Liabilities at fair value	(2.7)	(5.2)
Recurring | Not Designated as Hedging Instruments - Economic | Significant Other Observable Inputs (Level 2) | Foreign Exchange Forward Contracts
Fair Value Measurements
Assets at fair value	0.2	0.7
Liabilities at fair value	(2.7)	$ (5.2)
Nonrecurring
Fair Value Measurements
Assets at fair value, nonrecurring	4.8
Nonrecurring | Property Plant And Equipment At Fair Value [Member] | Boehlen Location [Member]
Fair Value Measurements
Assets at fair value, nonrecurring	3.3
Nonrecurring | Property Plant And Equipment At Fair Value [Member] | Schkopau PBR Location [Member]
Fair Value Measurements
Assets at fair value, nonrecurring	1.5
Nonrecurring | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurements
Assets at fair value, nonrecurring	4.8
Nonrecurring | Fair Value, Inputs, Level 3 [Member] | Property Plant And Equipment At Fair Value [Member] | Boehlen Location [Member]
Fair Value Measurements
Assets at fair value, nonrecurring	3.3
Nonrecurring | Fair Value, Inputs, Level 3 [Member] | Property Plant And Equipment At Fair Value [Member] | Schkopau PBR Location [Member]
Fair Value Measurements
Assets at fair value, nonrecurring	$ 1.5

Fair Value Measurements - Items

Fair Value Measurements - Items not at Fair Value (Details) - Significant Other Observable Inputs (Level 2) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Fair Value of Debt Instruments
Total fair value of long term debt	$ 1,126.3	$ 1,190.1
2025 Senior Notes
Fair Value of Debt Instruments
Total fair value of long term debt	476.1	503.7
2024 Term Loan B
Fair Value of Debt Instruments
Total fair value of long term debt	$ 650.2	$ 686.4

Provision for Income Taxes (Det

Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Provision for Income Taxes
Effective tax rate	101.50%	36.00%	47.20%	29.30%
Provision for income taxes	$ 64.7	$ 15.7	$ 52.8	$ 26.5

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure
Accrued obligations for environmental remediation and restoration costs	$ 0	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Purchase Commitments (Details)	6 Months Ended
	Jun. 30, 2020
Maximum
Loss Contingencies [Line Items]
Purchase commitment period	5 years
Minimum
Loss Contingencies [Line Items]
Purchase commitment period	1 year

Pension Plans and Other Postr_3

Pension Plans and Other Postretirement Benefits - Net Periodic Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net periodic benefit cost
Pension settlement loss				$ 0.7
Defined Benefit Pension Plans
Net periodic benefit cost
Service cost	$ 4.2	$ 3.1	$ 8.6	6.3
Interest cost	0.8	1.2	1.6	2.5
Expected return on plan assets	(0.3)	(0.5)	(0.6)	(1)
Amortization of prior service cost (credit)	(0.3)	(0.3)	(0.6)	(0.5)
Amortization of net (gain) loss	1.2	0.8	2.3	1.5
Pension settlement loss				0.7
Net periodic benefit cost	$ 5.6	$ 4.3	$ 11.3	$ 9.5
Interest cost, Statements of Operations location	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Expected return, Statements of Operations location	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Amortization of prior service credit, Statements of Operations location	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Amortization of gain (loss), Statements of Operations location	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Net settlement and curtailment loss, Statements of Operations location	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense	us-gaap:OtherNonoperatingIncomeExpense
Amounts recognized in other comprehensive income (loss)
Net periodic benefit cost	$ 5.6	$ 4.3	$ 11.3	$ 9.5
Other Postretirement Plans | Maximum
Net periodic benefit cost
Net periodic benefit cost	0.1	0.1	0.1	0.1
Amounts recognized in other comprehensive income (loss)
Net periodic benefit cost	$ 0.1	$ 0.1	$ 0.1	$ 0.1

Pension Plans and Other Postr_4

Pension Plans and Other Postretirement Benefits - Net Amounts Recognized (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Net amounts recognized in the balance sheets at December 31
Noncurrent liabilities	$ (276)	$ (276)	$ (270.6)
Cash contributions and benefit payments to unfunded plans	1.6	3.4
Expected contributions, remainder of current year	$ 4.5	$ 4.5

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 3.1	$ 3.5	$ 6.3	$ 7.7
Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	1.8	1.9	3.5	4
Unrecognized compensation cost	12.3		$ 12.3
Weighted-average period of recognition			2 years
Option Awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	0.8	0.8	$ 1.8	2
Unrecognized compensation cost, options	2.7		$ 2.7
Weighted-average period of recognition			1 year 4 months 24 days
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	0.5	$ 0.8	$ 1	$ 1.7
Unrecognized compensation cost	$ 3.7		$ 3.7
Weighted-average period of recognition			2 years 1 month 6 days

Share-Based Compensation - RSUs

Share-Based Compensation - RSUs (Details) - Restricted Share Units	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Other-than-Options, Shares Activity
Granted, Shares | shares	355,818
Other-than-Options, FV Activity
Granted, Weighted-Average Grant Date Fair Value per Share | $ / shares	$ 24.13

Share-Based Compensation - Opti

Share-Based Compensation - Options and PSUs (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Options, Additional Disclosures
Proceeds from exercise of option awards		$ 0.8
Option Awards
Options Outstanding Roll Forward
Granted, Options	530,241
Options, Additional Disclosures
Unrecognized compensation cost, options	$ 2.7
Fair Value Assumptions
Expected term (in years)	5 years 6 months
Expected volatility	39.93%
Risk-free interest rate	1.19%
Dividend yield	3.25%
Options granted, Weighted average grant date fair value	$ 6.51
Performance Share Units
Fair Value Assumptions
Expected term (in years)	3 years
Expected volatility	40.50%
Risk-free interest rate	1.16%
Share Price	$ 24.30
Other-than-Options, Shares Activity
Granted, Shares	102,545
Other-than-Options, FV Activity
Granted, Weighted-Average Grant Date Fair Value per Share	$ 24.54

Acquisitions and Divestitures -

Acquisitions and Divestitures - Acquisition (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Oct. 01, 2019
Acquisitions and Divestitures
Purchase price, net of cash acquired	$ (0.1)
Goodwill	67.7	$ 67.7
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Liabilities assumed			$ 2
Net cash received	$ 0.2	$ 6.7

Segments - Reconciliation of Se

Segments - Reconciliation of Segment Reporting to Consolidated (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)segment	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			6
Sales to external customers	$ 569.7	$ 951.8	$ 1,423.2	$ 1,964.9
Equity in earnings of unconsolidated affiliates	14.4	40.3	24.2	72.5
Adjusted EBITDA	9.4	123.6	88.3	251.7
Investment in unconsolidated affiliates	212.3		212.3		$ 188.1
Depreciation and amortization	$ 34.8	34.7	71.1	68.7
Capital expenditures			$ 48.2	47.6
Americas Styrenics
Segment Reporting Information [Line Items]
Percentage of ownership underlying net assets	50.00%		50.00%		50.00%
Investment in unconsolidated affiliates	$ 212.3		$ 212.3		$ 188.1
Latex Binders Segment
Segment Reporting Information [Line Items]
Sales to external customers	164.9	230.2	384	454.1
Latex Binders Segment | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	17	20.6	38.6	38.1
Synthetic Rubber Segment
Segment Reporting Information [Line Items]
Sales to external customers	36.4	112.1	138	236.7
Synthetic Rubber Segment | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	(27.7)	12.9	(12.5)	21.7
Performance Plastics Segment [Member]
Segment Reporting Information [Line Items]
Sales to external customers	189	347.5	494.2	716.8
Performance Plastics Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	(5.6)	34.2	31.2	69.9
Polystyrene [Member]
Segment Reporting Information [Line Items]
Sales to external customers	155.8	207.1	338.6	435.6
Polystyrene [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	14.8	16.2	26.6	32.9
Feedstocks [Member]
Segment Reporting Information [Line Items]
Sales to external customers	23.6	54.9	68.4	121.7
Feedstocks [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	(3.5)	(0.6)	(19.8)	16.6
Americas Styrenics [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 14.4	$ 40.3	$ 24.2	$ 72.5

Segments - Recon. of Net Income

Segments - Recon. of Net Income to Segment Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ (63.7)	$ 43.7	$ (111.9)	$ 90.3
Interest expense, net	(11.7)	(9.9)	(22)	(20.1)
Depreciation and amortization	34.8	34.7	71.1	68.7
Corporate Unallocated	17.7	20.8	39.6	46.9
Adjusted EBITDA addbacks	8.9	14.5	67.5	25.7
Adjusted EBITDA	9.4	123.6	88.3	251.7
Net (gain) loss on disposition of businesses and assets			(0.4)	(0.2)
Restructuring and other charges	6.3	(0.3)	8.1	0.1
Acquisition transactions and integration net costs (benefit)	(0.4)	0.7	(0.3)	0.7
Asset impairment charges or write-offs			38.3
Other items	3	14.1	21.8	25.1
Operating Segments [Member]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	(63.7)	43.7	(111.9)	90.3
Corporate Unallocated [Member]
Segment Reporting Information [Line Items]
Interest expense, net	$ (11.7)	$ (9.9)	$ (22)	$ (20.1)

Restructuring (Details)

Restructuring (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		24 Months Ended
	Jan. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		$ 7.5	$ (0.3)	$ 10.6	$ 0.1
Proceeds received on sale of property	$ 1.3					$ 12.5
Gain on sale of land				0.6
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	17.9			17.9
Expenses				7.1
Payments/Deductions				(7.9)
Accrued charges/Balance at end of period		17.1		17.1		17.9
Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		6.5		9.3
Cumulative life-to-date charges		27.1		27.1
Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.1	(0.4)	0.2	(0.2)
Cumulative life-to-date charges		6.3		6.3
Expected restructuring charges		1		1
Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			0.1	0.2	0.3
Cumulative life-to-date charges		24.8		24.8
Other Restructurings
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.9		0.9
Asset Impairment And Accelerated Depreciation [Member] | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		3.1		3.1
Asset Impairment And Accelerated Depreciation [Member] | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		14.7		14.7
Accelerated Depreciation | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.2		2.5
Cumulative life-to-date charges		2.9		2.9
Restructuring Reserve [Roll Forward]
Expenses		1.2
Employee Termination Benefit Charges
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	17.2			17.2
Expenses				6.7
Payments/Deductions				(7)
Accrued charges/Balance at end of period		16.9		16.9		17.2
Employee Termination Benefit Charges | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		4.1		4.4
Cumulative life-to-date charges		21.4		21.4
Restructuring Reserve [Roll Forward]
Expenses		4.1
Employee Termination Benefit Charges | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(0.4)		(0.4)
Cumulative life-to-date charges		0.7		0.7
Employee Termination Benefit Charges | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		5.4		5.4
Share-Based Compensation Benefit [Member] | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.4
Pension Benefits [Member] | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges		1		1
Contract Termination
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	$ 0.7			0.7
Payments/Deductions				(0.5)
Accrued charges/Balance at end of period		0.2		0.2		$ 0.7
Contract Termination | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.2		2.4
Cumulative life-to-date charges		2.8		2.8
Restructuring Reserve [Roll Forward]
Expenses		1.2
Contract Termination | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		0.3		0.3
Contract Termination | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		0.3		0.3
Decommissioning and Other Charges
Restructuring Reserve [Roll Forward]
Expenses				0.4
Payments/Deductions				(0.4)
Decommissioning and Other Charges | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.1		0.2	0.2
Cumulative life-to-date charges		2.2		2.2
Decommissioning and Other Charges | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 0.1	0.2	$ 0.3
Cumulative life-to-date charges		$ 4.4		$ 4.4

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Components (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	$ 603	$ 753.1	$ 668.9	$ 768.7
Balance at end of period	458.8	745.1	458.8	745.1
Cumulative Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(96)	(112.1)	(106.7)	(111.8)
Other comprehensive income (loss)	(1.1)	3	9.6	2.7
Balance at end of period	(97.1)	(109.1)	(97.1)	(109.1)
Pension and Other Postretirement Benefit Plans, Net
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(55.1)	(40.4)	(56.3)	(39.4)
Other comprehensive income (loss)			0.6	(2)
Amounts reclassified from AOCI to net income	0.5	0.3	1.1	1.3
Balance at end of period	(54.6)	(40.1)	(54.6)	(40.1)
Accumulated Gain Loss Net Cash Flow Hedge Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(3.1)	9	0.6	8.9
Other comprehensive income (loss)	(1.5)	(3.5)	(5.1)	(2.4)
Amounts reclassified from AOCI to net income	0.2	(1.9)	0.1	(2.9)
Balance at end of period	(4.4)	3.6	(4.4)	3.6
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(154.2)	(143.5)	(162.4)	(142.3)
Other comprehensive income (loss)	(2.6)	(0.5)	5.1	(1.7)
Amounts reclassified from AOCI to net income	0.7	(1.6)	1.2	(1.6)
Balance at end of period	$ (156.1)	$ (145.6)	$ (156.1)	$ (145.6)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Reclassification (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	$ 576.8		$ 865.6		$ 1,360.6	$ 1,781.2
Interest expense, net	11.7		9.9		22	20.1
Pension settlement loss						0.7
Income before income taxes	63.7		(43.7)		111.9	(90.3)
Provision for income taxes	64.7		15.7		52.8	26.5
Net income	128.4	$ 36.3	(28)	$ (35.8)	164.7	(63.8)
Pension and Other Postretirement Benefit Plans, Net | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pension settlement loss						0.7
Income before income taxes	0.8		0.5		1.7	1.7
Provision for income taxes	(0.3)		(0.2)		(0.6)	(0.4)
Net income	0.5		0.3		1.1	1.3
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior service credit	(0.3)		(0.3)		(0.6)	(0.6)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net actuarial loss	1.1		0.8		2.3	1.6
Accumulated Gain Loss Net Cash Flow Hedge Parent | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	(0.5)		(1.6)		(0.6)	(2.2)
Interest expense, net	0.7		(0.3)		0.7	(0.7)
Income before income taxes	0.2		(1.9)		0.1	(2.9)
Net income	$ 0.2		$ (1.9)		$ 0.1	$ (2.9)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings:
Net income (loss)	$ (128.4)	$ (36.3)	$ 28	$ 35.8	$ (164.7)	$ 63.8
Shares:
Weighted average ordinary shares outstanding	38.2		40.8		38.4	41
Dilutive effect of RSUs and option awards			0.3			0.5
Diluted weighted average ordinary shares outstanding	38.2		41.1		38.4	41.5
Income (loss) per share:
Income per share- basic	$ (3.36)		$ 0.69		$ (4.29)	$ 1.56
Income per share- diluted	$ (3.36)		$ 0.68		$ (4.29)	$ 1.54
Anti-dilutive shares excluded			0.7			0.8