Amphastar Pharmaceuticals (AMPH) 10-Q 10 Aug 20 2020 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Document and Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-36509
Entity Registrant Name	Amphastar Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0702205
Entity Address, Address Line One	11570 6th Street
Entity Address, City or Town	Rancho Cucamonga
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91730
City Area Code	909
Local Phone Number	980-9484
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	AMPH
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		47,485,546
Entity Central Index Key	0001297184
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 87,388	$ 73,685
Restricted cash	1,865	1,865
Short-term investments	11,101	11,675
Restricted short-term investments	2,200	2,290
Accounts receivable, net	49,862	45,376
Inventories	104,726	110,501
Income tax refunds and deposits	682	311
Prepaid expenses and other assets	8,997	9,538
Total current assets	266,821	255,241
Property, plant, and equipment, net	238,236	233,856
Finance lease right-of-use assets	774	887
Operating lease right-of-use assets	17,086	18,805
Goodwill and intangible assets, net	40,271	41,153
Other assets	12,635	11,156
Deferred tax assets	24,235	25,873
Total assets	600,058	586,971
Current Liabilities:
Accounts payable and accrued liabilities	75,385	77,051
Income taxes payable	2,345	2,042
Current portion of long-term debt	12,075	7,741
Current portion of operating lease liabilities	3,481	3,175
Total current liabilities	93,286	90,009
Long-term reserve for income tax liabilities	3,425	3,425
Long-term debt, net of current portion	34,622	39,394
Long-term operating lease liabilities, net of current portion	14,530	16,315
Deferred tax liabilities	760	867
Other long-term liabilities	10,998	9,433
Total liabilities	157,621	159,443
Stockholders' equity:
Preferred stock: par value $0.0001; 20,000,000 shares authorized; no shares issued and outstanding
Common stock: par value $0.0001; 300,000,000 shares authorized; 54,372,275 and 47,494,909 shares issued and outstanding as of June 30, 2020 and 52,495,483 and 46,576,968 shares issued and outstanding as of December 31, 2019, respectively	5	5
Additional paid-in capital	396,841	367,305
Retained earnings	120,127	116,370
Accumulated other comprehensive loss	(5,173)	(4,687)
Treasury stock	(114,119)	(97,627)
Total Amphastar Pharmaceuticals, Inc. stockholders' equity	397,681	381,366
Non-controlling Interests	44,756	46,162
Total equity	442,437	427,528
Total liabilities and stockholders' equity	$ 600,058	$ 586,971

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
CONDENSED CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock; shares authorized	300,000,000	300,000,000
Common stock; shares issued	54,372,275	52,495,483
Common stock; shares outstanding	47,494,909	46,576,968

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Net revenues	$ 85,806	$ 79,047	$ 170,494	$ 158,837
Cost of revenues	52,629	46,660	100,494	95,547
Gross profit	33,177	32,387	70,000	63,290
Operating (income) expenses:
Selling, distribution, and marketing	4,026	2,992	7,320	6,133
General and administrative	15,924	12,426	26,670	28,753
Research and development	16,149	15,996	31,452	30,603
Total operating expenses	36,099	31,414	65,442	65,489
Income (loss) from operations	(2,922)	973	4,558	(2,199)
Non-operating (expenses) income:
Interest income	198	143	351	291
Interest expense	(35)	(24)	(111)	(54)
Other income (expenses), net	1,255	60,001	(497)	59,422
Total non-operating (expenses) income, net	1,418	60,120	(257)	59,659
Income (loss) before income taxes	(1,504)	61,093	4,301	57,460
Income tax provision (benefit)	(75)	14,173	2,205	12,694
Net income (loss)	(1,429)	46,920	2,096	44,766
Net loss attributable to non-controlling interests	(1,237)	(867)	(1,661)	(3,889)
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.	$ (192)	$ 47,787	$ 3,757	$ 48,655
Net income (loss) per share attributable to Amphastar Pharmaceuticals, Inc. shareholders:
Basic (in Dollars per share)	$ 0	$ 1.01	$ 0.08	$ 1.04
Diluted (in Dollars per share)	$ 0	$ 0.96	$ 0.08	$ 0.97
Weighted-average shares used to compute net income (loss) per share attributable to Amphastar Pharmaceuticals, Inc. shareholders:
Basic (in Shares)	46,753	47,107	46,581	46,925
Diluted (in Shares)	46,753	49,894	48,458	50,155

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	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) attributable to Amphastar Pharmaceuticals, Inc.	$ (192)	$ 47,787	$ 3,757	$ 48,655
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc., net of income taxes
Foreign currency translation adjustment	288	(97)	(486)	(210)
Total other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.	288	(97)	(486)	(210)
Total comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.	$ 96	$ 47,690	$ 3,271	$ 48,445

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common stock	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total Amphastar Stockholders' Equity [Member]	Non-controlling Interest [Member]	Total
Balance at Dec. 31, 2018	$ 5	$ 344,434	$ 67,485	$ (4,013)	$ (75,476)	$ 332,435	$ 31,924
Balance at Dec. 31, 2018								$ 364,359
Balance at Dec. 31, 2018	51,438,675				(4,807,557)
Changes in Stockholders' Equity
Beginning balance adjustment as a result of the adoption of accounting standards			(54)			(54)		(54)
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			868			868		868
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(113)		(113)		(113)
Proceeds from the private placement of ANP		2,588				2,588	16,378	18,966
Net loss attributable to non-controlling interest							(3,022)	(3,022)
Treasury stock acquired					$ (3,015)	(3,015)		(3,015)
Treasury stock acquired (in Shares)					(145,479)
Issuance of treasury stock in connection with the Company's equity plans		(98)			$ 98
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					8,334
Issuance of common stock in connection with the Company's equity plans		(2,397)				(2,397)		(2,397)
Issuance of common stock in connection with the Company's equity plans (in Shares)	604,651
Share-based compensation expense		4,674				4,674		4,674
Balance at Mar. 31, 2019	$ 5	349,201	68,299	(4,126)	$ (78,393)	334,986	45,280
Balance at Mar. 31, 2019								380,266
Balance at Mar. 31, 2019	52,043,326				(4,944,702)
Balance at Dec. 31, 2018	$ 5	344,434	67,485	(4,013)	$ (75,476)	332,435	31,924
Balance at Dec. 31, 2018								364,359
Balance at Dec. 31, 2018	51,438,675				(4,807,557)
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.								48,655
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.								(210)
Balance at Jun. 30, 2019	$ 5	355,436	116,086	(4,223)	$ (79,459)	387,845	44,443
Balance at Jun. 30, 2019								432,288
Balance at Jun. 30, 2019	52,212,760				(4,995,085)
Balance at Mar. 31, 2019	$ 5	349,201	68,299	(4,126)	$ (78,393)	334,986	45,280
Balance at Mar. 31, 2019								380,266
Balance at Mar. 31, 2019	52,043,326				(4,944,702)
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			47,787			47,787		47,787
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(97)		(97)		(97)
Net loss attributable to non-controlling interest							(867)	(867)
Treasury stock acquired					$ (1,073)	(1,073)		(1,073)
Treasury stock acquired (in Shares)					(50,980)
Issuance of treasury stock in connection with the Company's equity plans		(7)			$ 7
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					597
Issuance of common stock in connection with the Company's equity plans		2,240				2,240		2,240
Issuance of common stock in connection with the Company's equity plans (in Shares)	169,434
Share-based compensation expense		4,002				4,002	30	4,032
Balance at Jun. 30, 2019	$ 5	355,436	116,086	(4,223)	$ (79,459)	387,845	44,443
Balance at Jun. 30, 2019								432,288
Balance at Jun. 30, 2019	52,212,760				(4,995,085)
Balance at Dec. 31, 2019	$ 5	367,305	116,370	(4,687)	$ (97,627)	381,366	46,162	381,366
Balance at Dec. 31, 2019								$ 427,528
Balance at Dec. 31, 2019	52,495,483				(5,918,515)			46,576,968
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			3,949			3,949		$ 3,949
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(774)		(774)		(774)
Net loss attributable to non-controlling interest							(424)	(424)
Treasury stock acquired					$ (10,950)	(10,950)		(10,950)
Treasury stock acquired (in Shares)					(647,246)
Issuance of treasury stock in connection with the Company's equity plans		(84)			$ 84
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					6,873
Issuance of common stock in connection with the Company's equity plans		(1,238)				(1,238)		(1,238)
Issuance of common stock in connection with the Company's equity plans (in Shares)	369,508
Share-based compensation expense		5,161				5,161	121	5,282
Balance at Mar. 31, 2020	$ 5	371,144	120,319	(5,461)	$ (108,493)	377,514	45,859
Balance at Mar. 31, 2020								423,373
Balance at Mar. 31, 2020	52,864,991				(6,558,888)
Balance at Dec. 31, 2019	$ 5	367,305	116,370	(4,687)	$ (97,627)	381,366	46,162	381,366
Balance at Dec. 31, 2019								$ 427,528
Balance at Dec. 31, 2019	52,495,483				(5,918,515)			46,576,968
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.								$ 3,757
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.								(486)
Balance at Jun. 30, 2020	$ 5	396,841	120,127	(5,173)	$ (114,119)	397,681	44,756	397,681
Balance at Jun. 30, 2020								$ 442,437
Balance at Jun. 30, 2020	54,372,275				(6,877,366)			47,494,909
Balance at Mar. 31, 2020	$ 5	371,144	120,319	(5,461)	$ (108,493)	377,514	45,859
Balance at Mar. 31, 2020								$ 423,373
Balance at Mar. 31, 2020	52,864,991				(6,558,888)
Changes in Stockholders' Equity
Net income (loss) attributable to Amphastar Pharmaceuticals, Inc.			(192)			(192)		(192)
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				288		288		288
Net loss attributable to non-controlling interest							(1,237)	(1,237)
Treasury stock acquired					$ (5,756)	(5,756)		(5,756)
Treasury stock acquired (in Shares)					(329,391)
Issuance of treasury stock in connection with the Company's equity plans		(130)			$ 130
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					10,913
Issuance of common stock in connection with the Company's equity plans		19,448				19,448		19,448
Issuance of common stock in connection with the Company's equity plans (in Shares)	1,507,284
Share-based compensation expense		6,379				6,379	134	6,513
Balance at Jun. 30, 2020	$ 5	$ 396,841	$ 120,127	$ (5,173)	$ (114,119)	$ 397,681	$ 44,756	397,681
Balance at Jun. 30, 2020								$ 442,437
Balance at Jun. 30, 2020	54,372,275				(6,877,366)			47,494,909

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows From Operating Activities:
Net income (loss)	$ 2,096	$ 44,766
Reconciliation to net cash provided by operating activities:
Loss (gain) on impairment and disposal of assets	30	850
Depreciation of property, plant, and equipment	9,531	8,311
Amortization of product rights, trademarks, and patents	509	526
Operating lease right-of-use asset amortization	1,700	1,390
Share-based compensation	11,795	8,706
Changes in deferred taxes, net	1,638	9,872
Changes in operating assets and liabilities:
Accounts receivable, net	(4,454)	1,700
Inventories	5,760	(30,012)
Prepaid expenses and other assets	541	(1,221)
Income tax refunds, deposits, and payables, net	(78)	1,784
Operating lease liabilities	(1,565)	(1,297)
Accounts payable and accrued liabilities	4,063	2,738
Net cash provided by operating activities	31,566	48,113
Cash Flows From Investing Activities:
Purchases and construction of property, plant, and equipment	(18,895)	(24,467)
Purchase of short-term investments	669
Payment of deposits and other assets	(562)	(86)
Net cash used in investing activities	(18,788)	(24,553)
Cash Flows From Financing Activities:
Proceeds from the private placement of ANP		18,298
Proceeds from equity plans, net of withholding tax payments	18,210
Proceeds from equity plans, net of withholding tax payments		(157)
Purchase of treasury stock	(16,706)	(4,088)
Proceeds from borrowing under lines of credit	705
Repayments under lines of credit		(347)
Proceeds from issuance of long-term debt	3,067
Principal payments on long-term debt	(4,269)	(3,219)
Net cash provided by (used in) financing activities	1,007	10,487
Effect of exchange rate changes on cash	(82)	(11)
Net increase (decrease) in cash, cash equivalents and restricted cash	13,703	34,036
Cash, cash equivalents, and restricted cash at beginning of period	75,550	88,202
Cash, cash equivalents, and restricted cash at end of period	89,253	122,238
Noncash Investing and Financing Activities:
Capital expenditure included in accounts payable	9,662	6,631
Operating lease right-of-use assets		7,671
Equipment acquired under finance leases	61	61
Supplemental Disclosures of Cash Flow Information:
Interest paid, net of capitalized interest	1,119	1,277
Income taxes paid	$ 662	$ 1,147

General

General	6 Months Ended
	Jun. 30, 2020
General
General	Note 1. General ​ Amphastar Pharmaceuticals, Inc., a Delaware corporation (together with its subsidiaries, hereinafter referred to as the “Company”) is a specialty pharmaceutical company that develops, manufactures, markets, and sells generic and proprietary injectable, inhalation, and intranasal products, including products with high technical barriers to market entry. Additionally, the Company sells insulin active pharmaceutical ingredient, or API, products. Most of the Company’s products are used in hospital or urgent care clinical settings and are primarily contracted and distributed through group purchasing organizations and drug wholesalers. The Company’s insulin API products are sold to other pharmaceutical companies for use in their own products and are being used by the Company in the development of injectable finished pharmaceutical products. The Company’s inhalation product, Primatene ® ​ The accompanying unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements of the Company for the year ended December 31, 2019 and the notes thereto as filed with the Securities and Exchange Commission, or SEC, in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with generally accepted accounting principles, or GAAP, have been condensed or omitted from the accompanying condensed consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from the audited financial statements. The accompanying interim financial statements are unaudited, but reflect all adjustments which are, in the opinion of management, necessary for a fair statement of the Company’s consolidated financial position, results of operations, comprehensive income (loss), stockholders’ equity, and cash flows for the periods presented. Unless otherwise noted, all such adjustments are of a normal, recurring nature. The Company’s results of operations, comprehensive income (loss) and cash flows for the interim periods are not necessarily indicative of the results of operations and cash flows that it may achieve in future periods.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with United States generally accepted accounting principles, or GAAP. All intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company. ​ The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Nanjing Letop Biological Technology Co., Ltd., or Letop, (5) Nanjing Hanxin Pharmaceutical Technology Co., Ltd., or Hanxin, (6) Nanjing Hanxin Biomedical Testing Service Co., Ltd., or Hanxin Biomedical, (7) Nanjing Baixin Trading Co. Ltd., or Baixin, (8) Amphastar France Pharmaceuticals, S.A.S., or AFP, (9) Amphastar UK Ltd., or AUK, and (10) International Medication Systems (UK) Limited, or IMS UK. ​ In July 2018, the Company’s Chinese subsidiary, ANP, completed a private placement of its common equity interest to accredited investors for aggregate gross proceeds of approximately $57 million, a portion of which was received in 2019. The Company has retained approximately 58% of the equity interest in ANP following the private placement and continues to consolidate the financial results of ANP with the Company’s results of operations. ANP’s net income after July 2, 2018, was attributed to the Company in accordance with the Company’s equity interest of approximately 58% in ANP. ​ ​ ​ ​ COVID-19 Pandemic ​ The Company is subject to risks and uncertainties as a result of the novel coronavirus pandemic, or COVID-19. The extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the response to the pandemic is in its initial stages and information is rapidly evolving. The Company considered the impact of COVID-19 on the assumptions and estimates used to determine the results reported and asset valuations as of June 30, 2020. ​ In March 2020, the World Health Organization declared the outbreak of a novel coronavirus, or COVID-19, as a pandemic, which continues to spread throughout the world, including locations where the Company operates, such as the United States, China and France. The Company has been actively monitoring the COVID-19 pandemic and its impact globally. In late January 2020, China implemented extensive curfews and travel restrictions to control the outbreak, and started easing these restrictions in March. Our business operations in China experienced a temporary disruption but resumed full operation in February 2020. In March 2020, France also implemented a stay-at-home order limiting movement and restricting travel, however, the Company was deemed to be an essential business and was not impacted by the restrictions. In March 2020, the Governors of the States of California and Massachusetts declared a health emergency and issued orders to close all nonessential business; as a specialty pharmaceutical company, the Company was deemed to be an essential businesses. In June 2020, some but not all of the restrictions were lifted in China, France, and states where the Company operates, and most businesses were allowed to reopen. All of the Company’s production facilities continued to operate during the quarter as they had prior to the COVID-19 pandemic with very little change, other than for enhanced safety measures intended to prevent the spread of the virus. ​ It is not possible at this time to estimate the complete impact that COVID-19 could have on the Company’s business, as the impact will depend on future developments, which are highly uncertain and cannot be predicted. Infections may resurge or become more widespread and the limitation on the Company’s ability to travel and timely sell and distribute its products, as well as any closures or supply disruptions, may be extended for longer periods of time, all of which would have a negative impact on the Company’s business, financial condition and operating results. The Company will continue to monitor the impact of COVID-19 on all aspects of its business. ​ Use of Estimates ​ The preparation of condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for credit losses, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to their net realizable values, impairment of long-lived and intangible assets and goodwill, workers’ compensation liabilities, litigation reserves, stock price volatilities for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions. ​ Foreign Currency ​ The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary, ANP, and its U.K. subsidiary, AUK, is the USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s condensed consolidated statements of operations. ​ The Company’s French subsidiary, AFP, maintains its book of record in euros. ANP’s Chinese subsidiaries maintain their books of record in Chinese yuan. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. These books of record are translated into USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature for the three months ended June 30, 2020, was $0.7 million gain and an immaterial loss for the six months ended June 30, 2020. For the three and six months ended June 30, 2019, the unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature was $0.4 million gain and $0.2 million loss, respectively. ​ Comprehensive Income (Loss) ​ For the three and six months ended June 30, 2020 and 2019, the Company included its foreign currency translation gain or loss as part of its comprehensive income (loss). There was no material income tax (benefit) expense allocated to other comprehensive income (loss) for the three and six months ended June 30, 2020 and 2019. ​ Advertising Expense ​ In connection with the launch of Primatene ® ​ Financial Instruments ​ The carrying amounts of cash and cash equivalents, short-term investments, restricted cash and short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. The majority of the Company’s long-term obligations consist of variable rate debt, and their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. The Company at times enters into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates without the exchange of the underlying notional debt amounts. Such interest rate swap contracts are recorded at their fair values. ​ Cash and Cash Equivalents ​ Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments purchased with original maturities of three months or less. ​ Short-Term Investments ​ Short-term investments as of June 30, 2020 and December 31, 2019 consisted of certificates of deposit and investment grade corporate bonds with original expiration dates within 12 months. ​ Restricted Cash ​ Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of June 30, 2020 and December 31, 2019, the restricted cash balance was $1.9 million. ​ Restricted Short-Term Investments ​ Restricted short-term investments consist of certificates of deposit that are collateral for standby letter of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months. As of June 30, 2020 and December 31, 2019, the balance of restricted short-term investments was $2.2 million and $2.3 million, respectively. ​ Deferred Income Taxes ​ The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. ​ Recent Accounting Pronouncements ​ In December 2019, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update, or ASU, No. 2019-12 Simplifying the Accounting for Income Taxes (Topic 740) ​ In April 2020, the FASB issued ASU No. 2020-04 Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting,

Revenue Recognition

Revenue Recognition	6 Months Ended
	Jun. 30, 2020
Revenue Recognition
Revenue Recognition	Note 3. Revenue Recognition ​ In accordance with Accounting Standard Codification, or ASC, 606 Revenue from Contacts with Customers ​ Generally, revenue is recognized at the time of product delivery to the Company’s customers. In some cases, revenue is recognized at the time of shipment when stipulated by the terms of the sale agreements. ​ The consideration the Company receives in exchange for its goods or services is only recognized when it is probable that a significant reversal will not occur. The consideration to which the Company expects to be entitled includes a stated list price, less various forms of variable consideration. The Company makes significant estimates for related variable consideration at the point of sale, including chargebacks, rebates, product returns, other discounts and allowances. ​ Provisions for estimated chargebacks, rebates, discounts, product returns and credit losses are made at the time of sale and are analyzed and adjusted, if necessary, at each balance sheet date. ​ Revenues derived from contract manufacturing services are recognized when third-party products are shipped to customers, and after the customer has accepted test samples of the products to be shipped. ​ The Company’s accounting policy is to review each agreement involving contract development and manufacturing services to determine if there are multiple revenue-generating activities that constitute more than one unit of accounting. Revenues are recognized for each unit of accounting based on revenue recognition criteria relevant to that unit. The Company does not have any revenue arrangements with multiple performance obligations. ​ Provision for Chargebacks and Rebates ​ The provision for chargebacks and rebates is a significant estimate used in the recognition of revenue. Wholesaler chargebacks relate to sales terms under which the Company agrees to reimburse wholesalers for differences between the gross sales prices at which the Company sells its products to wholesalers and the actual prices of such products that wholesalers resell under the Company’s various contractual arrangements with third parties such as hospitals and group purchasing organizations in the United States. Rebates include primarily amounts paid to retailers, payers, and providers in the United States, including those paid to state Medicaid programs, and are based on contractual arrangements or statutory requirements. The Company estimates chargebacks and rebates using the expected value method at the time of sale to wholesalers based on wholesaler inventory stocking levels, historic chargeback and rebate rates, and current contract pricing. ​ The provision for chargebacks and rebates is reflected as a component of net revenues. The following table is an analysis of the chargeback and rebate provision: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 21,644 $ 22,423 ​ Provision for chargebacks and rebates ​ 69,424 ​ 58,001 ​ Credits and payments issued to third parties ​ (72,625) ​ (61,704) ​ Ending balance ​ $ 18,443 ​ $ 18,720 ​ ​ Changes in the chargeback provision from period to period are primarily dependent on the Company’s sales to its wholesalers, the level of inventory held by wholesalers, and the wholesalers’ customer mix. Changes in the rebate provision from period to period are primarily dependent on retailer’s and other indirect customers’ purchases. The approach that the Company uses to estimate chargebacks has been consistently applied for all periods presented. Variations in estimates have been historically small. The Company continually monitors the provision for chargebacks and rebates and makes adjustments when it believes that the actual chargebacks and rebates may differ from the estimates. The settlement of chargebacks and rebates generally occurs within 30 days to 60 days after the sale to wholesalers. Accounts receivable and/or accounts payable and accrued liabilities are reduced and/or increased by the chargebacks and rebate amounts depending on whether the Company has the right to offset with the customer. Of the provision for chargebacks and rebates as of June 30, 2020 and December 31, 2019, $14.1 million and $15.4 million were included in accounts receivable, net, on the condensed consolidated balance sheets, respectively. The remaining provision as of June 30, 2020 and December 31, 2019 of $4.3 million and $6.2 million, respectively, were included in accounts payable and accrued liabilities. ​ Accrual for Product Returns ​ The Company offers most customers the right to return qualified excess or expired inventory for partial credit; however, API product sales are generally non-returnable. The Company’s product returns primarily consist of the returns of expired products from sales made in prior periods. Returned products cannot be resold. At the time product revenue is recognized, the Company records an accrual for product returns estimated using the expected value method. The accrual is based, in part, upon the historical relationship of product returns to sales and customer contract terms. The Company also assesses other factors that could affect product returns including market conditions, product obsolescence, and the introduction of new competition. Although these factors do not normally give the Company’s customers the right to return products outside of the regular return policy, the Company realizes that such factors could ultimately lead to increased returns. The Company analyzes these situations on a case-by-case basis and makes adjustments to the product return reserve as appropriate. ​ The provision for product returns is reflected as a component of net revenues. The following table is an analysis of the product return liability: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 10,339 $ 8,030 ​ Provision for product returns ​ 6,208 ​ 3,654 ​ Credits issued to third parties ​ (3,989) ​ (2,243) ​ Ending balance ​ $ 12,558 ​ $ 9,441 ​ ​ Of the provision of product returns as of June 30, 2020 and December 31, 2019, $8.3 million and $7.1 million, respectively, were included in accounts payable and accrued liabilities on the condensed consolidated balance sheets. The remaining provision as of June 30, 2020 and December 31, 2019, of $4.3 million and $3.2 million, respectively, were included in other long-term liabilities. For the six months ended June 30, 2020 and 2019, the Company’s aggregate product return rate was 1.3% and 1.5% of qualified sales, respectively.

(Loss) Income per Share Attribu

(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders	6 Months Ended
	Jun. 30, 2020
(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders
(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders	Note 4. (Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders ​ Basic net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders is calculated based upon the weighted-average number of shares outstanding during the period. Diluted net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders gives effect to all potential dilutive shares outstanding during the period, such as stock options, non-vested restricted stock units and shares issuable under the Company’s Employee Stock Purchase Plan, or ESPP and the reallocation of net income attributable to non-controlling interest from the assumed dilutive effect of stock options issued under the 2018 ANP Equity Incentive Plan, or the 2018 Plan. ​ As the Company reported a net loss for the three months ended June 30, 2020, the diluted net loss per share attributable to Amphastar Pharmaceuticals, Inc. shareholders, as reported, equals the basic net loss per share attributable to Amphastar Pharmaceuticals, Inc. shareholders since the effect of the assumed exercise of stock options, vesting of non-vested RSUs, and issuance of common shares under the Company’s ESPP are anti-dilutive. Total stock options, non-vested RSUs, and shares issuable under the Company’s ESPP excluded from the three months ended June 30, 2020 net loss per share were 8,887,036 stock options, 1,176,479 non-vested RSUs, and 60,386 shares issuable under the ESPP. ​ For the six months ended June 30, 2020, options to purchase 1,928,773 shares of stock, with a weighted-average exercise price of $20.84 per share, and the reallocation of net income attributable to non-controlling interest were excluded in the computation of diluted net income per common share attributable to Amphastar Pharmaceuticals, Inc.’s shareholders because the effect would be anti-dilutive. ​ For the three and six months ended June 30, 2019, options to purchase 783,001 and 762,937 shares of stock, respectively, with a weighted-average exercise price of $21.98 per share and $22.00 per share, respectively, and the reallocation of net income attributable to non-controlling interest were excluded in the computation of diluted net income per common share attributable to Amphastar Pharmaceuticals, Inc.’s shareholders because the effect would be anti-dilutive. ​ The following table provides the calculation of basic and diluted net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders for each of the periods presented: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands, except per share data) ​ Basic and dilutive numerator: ​ ​ ​ ​ Net (loss) income attributable to Amphastar Pharmaceuticals, Inc. ​ $ (192) ​ $ 47,787 ​ $ 3,757 ​ $ 48,655 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares outstanding — basic ​ 46,753 ​ 47,107 ​ 46,581 ​ 46,925 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Incremental shares from equity awards ​ — ​ 2,787 ​ 1,877 ​ 3,230 ​ Weighted-average shares outstanding — diluted ​ 46,753 ​ 49,894 ​ 48,458 ​ 50,155 ​ Net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders — basic ​ $ (0.00) ​ $ 1.01 ​ $ 0.08 ​ $ 1.04 ​ Net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders — diluted ​ $ (0.00) ​ $ 0.96 ​ $ 0.08 ​ $ 0.97 ​ ​

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 30, 2020
Segment Reporting
Segment Reporting	Note 5. Segment Reporting ​ The Company’s business is the development, manufacture, and marketing of pharmaceutical products. The Company has identified two reporting segments that each report to the Chief Operating Decision Maker, or CODM, as defined in ASC 280, Segment Reporting. The Company’s performance is assessed and resources are allocated by the CODM based on the following two reportable segments: ​ ● Finished pharmaceutical products ● API ​ The finished pharmaceutical products segment manufactures, markets and distributes Primatene ® Selected financial information by reporting segment is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Net revenues: ​ ​ ​ ​ Finished pharmaceutical products ​ $ 80,935 ​ $ 73,735 ​ $ 162,233 ​ $ 148,274 ​ API ​ 4,871 ​ 5,312 ​ 8,261 ​ ​ 10,563 ​ Total net revenues ​ 85,806 ​ 79,047 ​ 170,494 ​ 158,837 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finished pharmaceutical products ​ 35,437 ​ 34,540 ​ 74,247 ​ 66,852 ​ API ​ (2,260) ​ (2,153) ​ (4,247) ​ ​ (3,562) ​ Total gross profit ​ 33,177 ​ 32,387 ​ 70,000 ​ 63,290 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ 36,099 ​ 31,414 ​ 65,442 ​ 65,489 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Loss) income from operations ​ (2,922) ​ 973 ​ 4,558 ​ (2,199) ​ Non-operating expense ​ 1,418 ​ 60,120 ​ (257) ​ 59,659 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Loss) income before income taxes ​ $ (1,504) ​ $ 61,093 ​ $ 4,301 ​ $ 57,460 ​ ​ The Company manages its business segments to the gross profit level and manages its operating and other costs on a company-wide basis. The Company does not identify total assets by segment for internal purposes, as the Company’s CODM does not assess performance, make strategic decisions, or allocate resources based on assets. ​ The amount of net revenues in the finished pharmaceutical product segment is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Finished pharmaceutical products net revenues: ​ ​ ​ ​ ​ Primatene ® ​ $ 12,468 ​ $ 2,512 ​ $ 25,345 ​ $ 5,409 ​ Phytonadione ​ 10,689 ​ 12,441 ​ 21,718 ​ 22,561 ​ Enoxaparin ​ ​ 10,218 ​ ​ 9,838 ​ ​ 19,386 ​ ​ 24,322 ​ Lidocaine ​ ​ 7,608 ​ ​ 10,082 ​ ​ 18,265 ​ ​ 22,061 ​ Naloxone ​ ​ 8,723 ​ ​ 7,833 ​ ​ 17,598 ​ ​ 15,197 ​ Epinephrine ​ ​ 6,957 ​ ​ 3,139 ​ ​ 10,947 ​ ​ 5,818 ​ Other finished pharmaceutical products ​ 24,272 ​ 27,890 ​ 48,974 ​ 52,906 ​ Total finished pharmaceutical products net revenues ​ $ 80,935 ​ $ 73,735 ​ $ 162,233 ​ $ 148,274 ​ ​ ​ The amount of depreciation and amortization expense included in cost of revenue, by reporting segments, is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Depreciation and amortization expense ​ ​ ​ ​ Finished pharmaceutical products ​ $ 1,453 ​ $ 1,371 ​ $ 2,917 ​ $ 2,721 ​ API ​ 575 ​ 290 ​ 1,157 ​ ​ 575 ​ Total depreciation and amortization expense ​ $ 2,028 ​ $ 1,661 ​ $ 4,074 ​ $ 3,296 ​ ​ Net revenues and carrying values of long-lived assets of enterprises by geographic regions are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net Revenue ​ Long-Lived Assets ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ June 30, ​ June 30, ​ December 31, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) United States $ 81,898 $ 74,781 $ 162,963 $ 151,238 $ 106,301 $ 108,399 ​ China ​ 295 ​ 984 ​ 523 ​ 984 ​ 81,951 ​ 79,846 ​ France ​ 3,613 ​ 3,282 ​ 7,008 ​ ​ 6,615 ​ 49,984 ​ 45,611 ​ Total ​ $ 85,806 ​ $ 79,047 ​ $ 170,494 ​ $ 158,837 ​ $ 238,236 ​ $ 233,856 ​ ​

Customer and Supplier Concentra

Customer and Supplier Concentration	6 Months Ended
	Jun. 30, 2020
Customer and Supplier Concentration
Customer and Supplier Concentration	Note 6. Customer and Supplier Concentration ​ Customer Concentrations ​ Three large wholesale drug distributors, AmerisourceBergen Corporation, or AmerisourceBergen, Cardinal Health, Inc., or Cardinal, and McKesson Corporation, or McKesson, are all distributors of the Company’s products as well as suppliers of a broad range of health care products. The Company considers these three customers to be its major customers, as each individually, and these customers collectively, represented a significant percentage of the Company’s net revenue for the three and six months ended June 30, 2020 and 2019, and accounts receivable as of June 30, 2020 and December 31, 2019, respectively. The following table provides accounts receivable and net revenue information for these major customers: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % of Total Accounts ​ % of Net ​ ​ Receivable ​ Revenue ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ December 31, ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 2020 2019 AmerisourceBergen 9 % 13 % 23 % 25 % 23 % 23 % McKesson 22 % 34 % 23 % 25 % 23 % 27 % Cardinal Health 22 % 17 % 19 % 21 % 19 % 23 % ​ Supplier Concentrations ​ The Company depends on suppliers for raw materials, APIs, and other components that are subject to stringent FDA requirements. Some of these materials may only be available from one or a limited number of sources. Establishing additional or replacement suppliers for these materials may take a substantial period of time, as suppliers must be approved by the FDA. Furthermore, a significant portion of raw materials may only be available from foreign sources. If the Company is unable to secure, on a timely basis, sufficient quantities of the materials it depends on to manufacture and market its products, it could have a materially adverse effect on the Company’s business, financial condition, and results of operations.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Measurements
Fair Value Measurements	Note 7. Fair Value Measurements ​ GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal or most advantageous market for the asset or liability at the measurement date (an exit price). These standards also establish a hierarchy that prioritizes observable and unobservable inputs used in measuring fair value of an asset or liability, as described below: ​ ● Level 1 – Inputs to measure fair value are based on quoted prices (unadjusted) in active markets on identical assets or liabilities; ​ ● Level 2 – Inputs to measure fair value are based on the following: a) quoted prices in active markets on similar assets or liabilities, b) quoted prices for identical or similar instruments in inactive markets, or c) observable (other than quoted prices) or collaborated observable market data used in a pricing model from which the fair value is derived; and ​ ● Level 3 – Inputs to measure fair value are unobservable and the assets or liabilities have little, if any, market activity; these inputs reflect the Company’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities based on best information available in the circumstances. ​ As of June 30, 2020, cash equivalents include money market accounts. Short-term investments consist of certificates of deposit as well as investment-grade corporate bonds with original expiration dates within 12 months. The certificates of deposit are carried at amortized cost in the Company’s condensed consolidated balance sheet, which approximates their fair value determined based on Level 2 inputs. The corporate bonds are classified as held-to-maturity and are carried at amortized cost net of an allowance for credit losses, which approximates their fair value determined based on Level 2 inputs. The restrictions on restricted cash and short-term investments have a negligible effect on the fair value of these financial assets. ​ The fair value of the Company’s financial assets and liabilities measured on a recurring basis as of June 30, 2020 and December 31, 2019, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) Cash equivalents - money market ​ $ 62,525 ​ $ 62,525 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 1,865 ​ ​ 1,865 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 9,079 ​ ​ — ​ ​ 9,079 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate bonds ​ ​ 2,010 ​ ​ — ​ ​ 2,010 ​ ​ — ​ Fair value measurement as of June 30, 2020 ​ $ 77,679 ​ $ 64,390 ​ $ 13,289 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market ​ $ 29,521 ​ $ 29,521 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 1,865 ​ ​ 1,865 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 8,867 ​ ​ — ​ ​ 8,867 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,290 ​ — ​ 2,290 ​ — ​ Corporate bonds ​ ​ 2,789 ​ ​ — ​ ​ 2,789 ​ ​ — ​ Fair value measurement as of December 31, 2019 ​ $ 45,332 ​ $ 31,386 ​ $ 13,946 ​ $ — ​ ​ The Company does not hold any Level 3 instruments that are measured at fair value on a recurring basis. ​ Nonfinancial assets and liabilities are not measured at fair value on a recurring basis but are subject to fair value adjustments in certain circumstances. These items primarily include long-lived assets, goodwill, and intangible assets for which the fair value of assets is determined as part of the related impairment test. As of June 30, 2020 and December 31, 2019, there were no adjustments to fair value for nonfinancial assets or liabilities.

Investments

Investments	6 Months Ended
	Jun. 30, 2020
Investments
Investments	Note 8. Investments ​ A summary of the Company’s investments that are classified as held-to-maturity is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) Corporate bonds ​ $ 2,005 ​ $ 5 ​ $ — ​ $ 2,010 Total investments as of June 30, 2020 ​ $ 2,005 ​ $ 5 ​ $ — ​ $ 2,010 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ $ 2,790 ​ $ — ​ $ (1) ​ $ 2,789 Total investments as of December 31, 2019 ​ $ 2,790 ​ $ — ​ $ (1) ​ $ 2,789 ​ The Company believes that the unrealized gains and losses disclosed above were primarily driven by interest rate change rather than by unfavorable changes in the credit ratings associated with these securities and as a result, the Company continues to expect to collect the principal and interest due on its debt securities that have an amortized cost in excess of fair value. At each reporting period, the Company evaluates securities for impairment when the fair value of the investment is less than its amortized cost. The Company evaluated the underlying credit quality and credit ratings of the issuers, noting neither a significant deterioration since purchase nor any other factors that would indicate a material credit loss. ​ The Company measures expected credit losses on held-to-maturity investments on a collective basis. All the Company’s held-to-maturity investments were considered to be one pool. The estimate for credit losses considers historical loss information that is adjusted for current conditions and reasonable and supportable forecasts. Expected credit losses on held-to-maturity investments were not material to the condensed consolidated financial statements.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets
Goodwill and Intangible Assets	Note 9. Goodwill and Intangible Assets ​ The table below shows the weighted-average life, original cost, accumulated amortization, and net book value by major intangible asset classification: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 8,625 ​ $ 3,378 ​ $ 5,247 ​ Patents 12 ​ 486 ​ ​ 276 ​ 210 ​ Land-use rights 39 ​ 2,540 ​ ​ 584 ​ 1,956 ​ Subtotal 12 ​ 11,651 ​ 4,238 ​ 7,413 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,633 ​ — ​ 3,633 ​ Subtotal * ​ 32,858 ​ — ​ 32,858 ​ As of June 30, 2020 * ​ $ 44,509 ​ $ 4,238 ​ $ 40,271 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,226 ​ $ 3,152 ​ $ 6,074 ​ Patents 12 ​ 486 ​ 255 ​ 231 ​ Land-use rights 39 ​ 2,540 ​ 551 ​ 1,989 ​ Other intangible assets 4 ​ 69 ​ 69 ​ — ​ Subtotal 12 ​ 12,321 ​ 4,027 ​ 8,294 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,634 ​ — ​ 3,634 ​ Subtotal * ​ 32,859 ​ — ​ 32,859 ​ As of December 31, 2019 * ​ $ 45,180 ​ $ 4,027 ​ $ 41,153 ​ * Intangible assets with indefinite lives have an indeterminable average life. ​ Goodwill ​ The changes in the carrying amounts of goodwill were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 3,634 $ 3,951 ​ Currency translation ​ (1) ​ (317) ​ Ending balance ​ $ 3,633 ​ $ 3,634 ​ ​ Primatene ® Trademark ​ In January 2009, the Company acquired the exclusive rights to the trademark, domain name, website and domestic marketing, distribution and selling rights related to Primatene ® ​ The trademark was determined to have an indefinite life. In determining its indefinite life, the Company considered the following: the expected use of the intangible; the longevity of the brand; the legal, regulatory and contractual provisions that affect their maximum useful life; the Company’s ability to renew or extend the asset’s legal or contractual life without substantial costs; effects of the regulatory environment; expected changes in distribution channels; maintenance expenditures required to obtain the expected future cash flows from the asset; and considerations for obsolescence, demand, competition and other economic factors.

Inventories

Inventories	6 Months Ended
	Jun. 30, 2020
Inventories
Inventories	Note 10. Inventories ​ Inventories consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Raw materials and supplies $ 50,657 $ 59,233 ​ Work in process ​ 39,169 ​ 35,548 ​ Finished goods ​ 14,900 ​ 15,720 ​ Total inventories ​ $ 104,726 ​ $ 110,501 ​ ​ ​ ​ Charges totaling $8.1 million and $10.2 million were included in the cost of revenues in the Company’s condensed consolidated statements of operations for the three and six months ended June 30, 2020, respectively, to adjust the Company’s inventory and related firm inventory purchase commitments to their net realizable value. For the three and six months ended June 30, 2019, charges totaling $2.5 million and $5.7 million were included in the cost of revenues, respectively, to adjust the Company’s inventory and related firm inventory purchase commitments to their net realizable value.

Property, Plant, and Equipment

Property, Plant, and Equipment	6 Months Ended
	Jun. 30, 2020
Property, Plant, and Equipment
Property, Plant, and Equipment	Note 11. Property, Plant, and Equipment ​ Property, plant, and equipment consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Buildings $ 119,648 $ 117,928 ​ Leasehold improvements ​ 29,510 ​ 29,531 ​ Land ​ 7,604 ​ 7,603 ​ Machinery and equipment ​ 174,308 ​ 164,802 ​ Furniture, fixtures, and automobiles ​ 24,787 ​ 22,043 ​ Construction in progress ​ 55,832 ​ 56,354 ​ Total property, plant, and equipment ​ 411,689 ​ 398,261 ​ Less accumulated depreciation ​ (173,453) ​ (164,405) ​ Total property, plant, and equipment, net ​ $ 238,236 ​ $ 233,856 ​ ​

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	6 Months Ended
	Jun. 30, 2020
Accounts Payable and Accrued Liabilities.
Accounts Payable and Accrued Liabilities	Note 12. Accounts Payable and Accrued Liabilities ​ Accounts payable and accrued liabilities consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 ​ (in thousands) Accrued customer fees and rebates $ 9,049 ​ $ 9,633 Accrued payroll and related benefits ​ 23,134 ​ ​ 21,872 Accrued product returns, current portion ​ 8,326 ​ ​ 7,126 Accrued loss on firm purchase commitments ​ 5,520 ​ ​ 3,352 Other accrued liabilities ​ 7,648 ​ ​ 10,007 Total accrued liabilities 53,677 ​ 51,990 Accounts payable 21,708 ​ 25,061 Total accounts payable and accrued liabilities $ 75,385 ​ $ 77,051 ​

Debt

Debt	6 Months Ended
	Jun. 30, 2020
Debt
Debt	Note 13. Debt ​ Debt consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Loans with East West Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due December 2020 ​ $ — ​ $ — ​ Mortgage payable due February 2021 ​ ​ 3,354 ​ ​ 3,401 ​ Equipment loan due June 2021 ​ ​ 1,224 ​ ​ 1,837 ​ Equipment loan due December 2022 ​ ​ 5,000 ​ ​ 6,000 ​ Equipment loan due February 2024 ​ ​ 6,084 ​ ​ 3,570 ​ Mortgage payable due October 2026 ​ ​ 3,367 ​ ​ 3,400 ​ Mortgage payable due June 2027 ​ ​ 8,586 ​ ​ 8,659 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans with Cathay Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due May 2022 ​ — ​ — ​ Acquisition loan due June 2024 ​ 9,833 ​ 10,928 ​ Mortgage payable due August 2027 ​ 7,361 ​ 7,452 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans with Seine-Normandie Water Agency ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ French government loan due June 2020 ​ ​ — ​ ​ 28 ​ French government loan due July 2021 ​ ​ 118 ​ ​ 114 ​ French government loans due December 2026 ​ ​ 380 ​ ​ 374 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loan with China Everbright Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due June 2021 ​ ​ 707 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Payment Obligation to Merck ​ — ​ 561 ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment under Finance Leases ​ 683 ​ 811 ​ Total debt ​ 46,697 ​ 47,135 ​ Less current portion of long-term debt ​ 12,075 ​ 7,741 ​ Long-term debt, net of current portion ​ $ 34,622 ​ $ 39,394 ​ ​ As of June 30, 2020, the fair value of the loans listed above approximated their carrying amount. The interest rate used in the fair value estimation was determined to be a Level 2 input. For certain loans with East West Bank, the Company has entered into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates over the life of certain debt instruments without the exchange of the underlying notional debt amount. The interest rate swap contracts do not qualify for hedge accounting and are recorded at fair value based on Level 2 inputs. These swap contracts were all in a liability position with an aggregate fair value of $1.2 million and $0.4 million as of June 30, 2020 and December 31, 2019, respectively. The change in fair value is recorded in other income (expense) in the Company’s condensed consolidated statement of operations. ​ ​ Loans with Cathay Bank ​ Line of Credit Facility—Due May 2022 ​ In June 2020, the Company amended the $20.0 million revolving line of credit facility. The amendment was effective in June 2020. Under the amended line of credit facility, the maturity date was extended to May 2022, and bears a variable interest rate at the prime rate as published by The Wall Street Journal outstanding ​ Loan with China Everbright Bank ​ Line of Credit Facility – Due June 2021 ​ In June 2020, the Company entered into a line of credit facility for $0.7 million. The loan bears interest at a fixed rate of 4.05%. Interest payments are due quarterly and repayment of the principle amount is due in June 2021. As of June 30, 2020, the Company had $0.7 million outstanding under this loan. ​ Credit Agreement with China Merchant Bank ​ In March 2020, the Company entered into a credit agreement with China Merchant Bank. The credit agreement allows the Company to borrow up to $14.0 million secured by buildings and land use rights held by ANP. The interest rate and other terms will be determined at the time of the borrowing, depending on the type of loan requested. The credit period is for 36 months and expires in March 2023. No amounts have been borrowed under this credit agreement as of June 30, 2020. ​ Covenants ​ At June 30, 2020 and December 31, 2019, the Company was in compliance with its debt covenants.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Taxes
Income Taxes	Note 14. Income Taxes ​ The following table sets forth the Company’s income tax (benefit) provision for the periods indicated: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2020 2019 2020 2019 ​ ​ (in thousands) (Loss) income before taxes ​ $ (1,504) ​ $ 61,093 ​ $ 4,301 ​ $ 57,460 ​ Income tax (benefit) provision ​ ​ (75) ​ 14,173 ​ ​ 2,205 ​ 12,694 ​ Net (loss) income ​ $ (1,429) ​ $ 46,920 ​ $ 2,096 ​ $ 44,766 ​ Income tax (benefit) provision as a percentage of (loss) income before income taxes ​ ​ 5.0 % 23.2 % ​ 51.3 % 22.1 % ​ The change in the Company’s effective tax rate for the three and six months ended June 30, 2020, was primarily due to differences in pre-tax (loss) income positions, nondeductible executive severance compensation, and timing of discrete tax items. ​ CARES Act ​ The Coronavirus Aid, Relief, and Economic Security Act, or the CARES Act, became law on March 27, 2020. It provides additional economic stimulus to address the impact of the COVID-19 pandemic. The Company does not expect there to be any significant benefit to its income tax provision as a result of the CARES Act, and will continue to closely monitor the impact of the COVID-19 pandemic, as well as any effects that may result from the CARES Act or future legislation. ​ Valuation Allowance ​ In assessing the need for a valuation allowance, management considers whether it is more likely than not that some portion or all of the deferred tax assets will be realized. Ultimately, the realization of deferred tax assets depends on the existence of future taxable income. Management considers sources of taxable income such as income in prior carryback periods, future reversal of existing deferred taxable temporary differences, tax-planning strategies, and projected future taxable income. ​ The Company continues to record a full valuation allowance on AFP’s income tax benefits and will continue to do so until AFP generates sufficient taxable income to realize its deferred income tax assets ​ For purposes of computing its annual effective tax rate, the Company did not benefit from its losses in the states where it files separately. This increased the Company’s income tax benefit by an immaterial amount during the three months ended June 30, 2020 and increased its income tax provision $0.2 million for the six months ended June 30, 2020.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2020
Stockholders' Equity
Stockholders' Equity	Note 15. Stockholders' Equity ​ Share Buyback Program ​ Pursuant to the Company’s existing share buyback program, the Company purchased 329,391 and 976,106 shares of its common stock during the three and six months ended June 30, 2020, for total consideration of $5.8 million and $16.7 million, respectively. The Company purchased 50,980 and 196,459 shares of its common stock during the three and six months ended June 30, 2019, for total consideration of $1.1 million and $4.1 million, respectively. ​ In August 2020, the Company’s Board of Directors authorized an increase of $20.0 million to the Company’s share buyback program, which is expected to continue for an indefinite period of time. The primary goal of the program is to offset dilution created by the Company’s equity compensation programs. ​ Purchases are made through open market and private block transactions pursuant to Rule 10b5-1 plans, privately negotiated transactions or other means as determined by the Company’s management and in accordance with the requirements of the SEC and applicable laws. The timing and actual number of treasury share purchases will depend on a variety of factors including price, corporate and regulatory requirements, and other conditions. These treasury share purchases are accounted for under the cost method and are included as a component of treasury stock in the Company’s condensed consolidated balance sheets. ​ 2015 Equity Incentive Plan ​ As of June 30, 2020, the Company reserved an aggregate of 6,353,582 shares of common stock for future issuance under the 2015 Equity Incentive Plan, or the 2015 Plan, including 1,164,425 shares that were reserved in January 2020 pursuant to the evergreen provision in the 2015 Plan. ​ 2014 Employee Stock Purchase Plan ​ As of June 30, 2020, the Company has issued 738,780 shares of common stock under the ESPP, and 1,261,220 shares of its common stock remains available for issuance under the ESPP. ​ During the three months ended June 30, 2020, the Company issued 79,245 shares at a weighted-average purchase price of $15.84 per share under the ESPP. For the three and six months ended June 30, 2020, the Company recorded ESPP, expense of $0.3 million and $0.4 million, respectively. For the three and six months ended June 30, 2019, the Company recorded ESPP expense of $0.2 million and $0.3 million, respectively. ​ Share-Based Award Activity and Balances (excluding the ANP Equity Plan) ​ The Company accounts for share-based compensation payments in accordance with ASC 718, which requires measurement and recognition of compensation expense at fair value for all share-based payment awards made to employees and directors. Under these standards, the fair value of option awards and the option components of the Employee Stock Purchase Plan awards are estimated at the grant date using the Black-Scholes option-pricing model. The fair value of RSUs is estimated at the grant date using the Company’s common share price. The portion that is ultimately expected to vest is amortized and recognized in compensation expense on a straight-line basis over the requisite service period, generally from the grant date to the vesting date. ​ The weighted-averages for key assumptions used in determining the fair value of options granted during 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 ​ Average volatility 44.0 % 43.4 % 43.1 % 42.5 % ​ Risk-free interest rate 0.5 % 2.0 % 0.8 % 2.4 % ​ Weighted-average expected life in years 4.9 ​ 5.0 ​ 5.7 ​ 5.7 ​ ​ Dividend yield rate — % — % — % — % ​ ​ A summary of option activity for the six months ended June 30, 2020, is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term (Years) ​ Value (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Outstanding as of December 31, 2019 9,763,485 $ 15.26 ​ ​ Options granted 1,789,254 ​ 13.52 ​ ​ ​ ​ ​ ​ Options exercised (1,473,323) ​ 14.22 ​ ​ ​ ​ ​ ​ Options cancelled (84,203) ​ 16.53 ​ ​ ​ ​ ​ ​ Options expired (1,108,177) ​ 16.45 ​ ​ ​ ​ ​ ​ Outstanding as of June 30, 2020 8,887,036 ​ $ 14.92 5.65 ​ $ 66,980 ​ Exercisable as of June 30, 2020 6,029,545 ​ $ 14.31 4.41 ​ $ 49,123 ​ (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the estimated fair value of the Company’s common stock for those awards that have an exercise price below the estimated fair value at June 30, 2020. ​ For the three and six months ended June 30, 2020, the Company recorded an expense of $2.6 million and $5.2 million, respectively, related to stock options granted. For the three and six months ended June 30, 2019, the Company recorded an expense of $1.8 million and $4.2 million, respectively, related to stock options granted under all plans. ​ In April 2020, Jason Shandell resigned from his position as the Company’s President and General Counsel and as a member of the Company’s board of directors. In connection with his resignation, the Company and Mr. Shandell entered into a separation agreement. As part of the separation agreement, the Company agreed to accelerate 80% of his unvested stock options and extended the expiration date of certain vested stock option awards. As a result of this modification, the Company incurred an expense of $0.7 million, which is included as part of share-based compensation expense within general and administration expenses in the condensed consolidated statement of operations during the three and six months ended June 30, 2020. ​ Information relating to option grants and exercises is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 ​ ​ (in thousands, except per share data) Weighted-average grant date fair value per option share ​ $ 7.15 ​ $ 8.17 ​ $ 5.48 ​ $ 8.46 ​ Intrinsic value of options exercised ​ 6,486 ​ 452 ​ 6,974 ​ 5,822 ​ Cash received from options exercised ​ 19,088 ​ 1,108 ​ 20,339 ​ 5,047 ​ Total fair value of the options vested during the year ​ 2,411 ​ 388 ​ 9,844 ​ 7,502 ​ ​ A summary of the status of the Company’s non-vested options as of June 30, 2020, and changes during the six months ended June 30, 2020, is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ Options ​ Fair Value Non-vested as of December 31, 2019 ​ 2,747,133 ​ $ 6.99 ​ Options granted 1,789,254 ​ 5.48 ​ Options vested (1,594,693) ​ 6.17 ​ Options forfeited (84,203) ​ 7.13 ​ Non-vested as of June 30, 2020 2,857,491 ​ 6.50 ​ ​ As of June 30, 2020, there was $14.6 million of total unrecognized compensation cost, net of forfeitures, related to non-vested stock option based compensation arrangements granted. The cost is expected to be recognized over a weighted-average period of 2.5 years and will be adjusted for future changes in estimated forfeitures. ​ Restricted Stock Units ​ The Company grants restricted stock units, or RSUs, to certain employees and members of the Board of Directors with a vesting period of up to five years. The grantee receives one share of common stock at a specified future date for each RSU awarded. The RSUs may not be sold or otherwise transferred until certificates of common stock have been issued, recorded, and delivered to the participant. The RSUs do not have any voting or dividend rights prior to the issuance of certificates of the underlying common stock. The share-based expense associated with these grants was based on the Company’s common stock fair value at the time of grant and is amortized over the requisite service period, which generally is the vesting period using the straight-line method. During the three and six months ended June 30, 2020, the Company recorded a total expense of $3.6 million and $6.0 million, respectively, related to RSU awards granted. During the three and six months ended June 30, 2019, the Company recorded expenses of $2.0 million and $4.1 million, respectively, related to RSU awards granted. ​ As part of the separation agreement with Mr. Shandell, the Company agreed to accelerate the vesting of 80% of his RSU awards. As a result of this modification, the Company incurred an expense of $1.6 million, which is included as part of share-based compensation within general and administrative expenses in the condensed consolidated statement of operations during the three and six months ended June 30, 2020. ​ As of June 30, 2020, there was $15.9 million of total unrecognized compensation cost, net of forfeitures, related to non-vested RSU-based compensation arrangements granted. The cost is expected to be recognized over a weighted-average period of 2.5 years and will be adjusted for future changes in estimated forfeitures. ​ Information relating to RSU grants and deliveries is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Market ​ ​ ​ ​ Value of RSUs ​ ​ ​ ​ Issued ​ ​ Total RSUs ​ as ​ Issued Compensation (1) ​ ​ ​ ​ (in thousands) RSUs outstanding at December 31, 2019 1,099,496 ​ ​ ​ ​ RSUs granted 727,746 ​ $ 9,811 ​ RSUs forfeited (35,792) ​ ​ ​ ​ RSUs vested (2) (614,971) ​ ​ ​ ​ RSUs outstanding at June 30, 2020 1,176,479 ​ ​ ​ ​ (1) The total fair market value is derived from the number of RSUs granted times the stock price on the date of grant. (2) Of the vested RSUs, 235,053 shares of common stock were surrendered to fulfill tax withholding obligations. ​ The 2018 ANP Equity Incentive Plan ​ In December 2018, ANP’s board of directors approved the 2018 Plan, which is set to expire in December 2023. The 2018 Plan permits the grant of stock options and other equity awards in ANP shares to ANP employees. As of June 30, 2020, ANP has issued 2,433,445 stock options and issued 3,648,932 stock options in 2019, to its employees under the 2018 Plan. As of June 30, 2020, the number of stock options outstanding was 5,918,777 . The options vest over a period of approximately four years and have up to a 10 year contractual term. For the three and six months ended June 30, 2020, the Company recorded expense of $0.2 million and $0.3 million related to stock options issued by ANP under the 2018 Plan, respectively. For the three and six months ended June 30, 2019, the Company recorded an immaterial amount of expense related to stock options issued by ANP under the 2018 Plan. ​ The Company recorded the aggregated share-based compensation expense in the consolidated statement of operations as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 2019 ​ ​ (in thousands) Cost of revenues $ 970 $ 959 $ 2,329 $ 2,238 ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Selling, distribution, and marketing ​ 123 ​ 95 ​ 230 ​ 189 ​ General and administrative ​ 5,052 ​ 2,648 ​ 8,271 ​ 5,439 ​ Research and development ​ 368 ​ 330 ​ 965 ​ 840 ​ Total share-based compensation ​ $ 6,513 ​ $ 4,032 ​ $ 11,795 ​ $ 8,706 ​ ​ ​

Employee Benefits

Employee Benefits	6 Months Ended
	Jun. 30, 2020
Employee Benefits
Employee Benefits	Note 16. Employee Benefits ​ 401(k) Plan ​ The Company has a defined contribution 401(k) plan, or the Plan, whereby eligible employees voluntarily contribute up to a defined percentage of their annual compensation. The Company matches contributions at a rate of 50% on the first 6% of employee contributions, and pays the administrative costs of the Plan. Total employer contributions for the three and six months ended June 30, 2020 were approximately $0.5 million and $1.0 million, respectively, compared to the prior year expense of $0.4 million and $0.7 million for the three and six months ended June 30, 2019, respectively. ​ Defined Benefit Pension Plan ​ The Company’s subsidiary, AFP, has an obligation associated with a defined-benefit plan for its eligible employees. This plan provides benefits to the employees from the date of retirement and is based on the employee’s length of time employed by the Company. The calculation is based on a statistical calculation combining a number of factors that include the employee’s age, length of service, and AFP employee turnover rate. ​ The liability under the plan is based on a discount rate of 0.9% as of June 30, 2020 and December 31, 2019, respectively. The liability is included in accrued liabilities in the accompanying condensed consolidated balance sheets. The plan is currently unfunded, and the benefit obligation under the plan was $2.5 million and $2.4 million at June 30, 2020 and December 31, 2019, respectively. The Company recorded an immaterial amount of expense under the plan for the three and six months ended June 30, 2020 and 2019. ​ Deferred Compensation Plan ​ In December 2019, the Company established a non-qualified deferred compensation plan. The deferred compensation plan allows certain eligible participants to defer a portion of their cash compensation and provides a matching contribution at the discretion of the Company. The plan’s obligations are payable upon retirement, termination of employment and/or certain other times in a lump-sum distribution or in installments, as elected by the participant in accordance with the plan. Participants can allocate their deferred compensation amongst various investment options with earnings accruing to the participant. The Company has established a Rabbi Trust to fund the plan obligations and to hold the plan assets. Eligible participants began contributing to the plan in January 2020. As of June 30, 2020, the plan assets and liabilities

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies
Commitments and Contingencies	Note 17. Commitments and Contingencies ​ Purchase Commitments ​ As of June 30, 2020, the Company has entered into commitments to purchase equipment and raw materials for an aggregate amount of approximately $50.0 million. The Company anticipates that most of these commitments with remaining terms in excess of one year will be fulfilled by the end of 2021. ​ In accordance with certain agreements between ANP and the Chinese government, in January 2010 and November 2012, the Company acquired certain land-use rights for $1.2 million and $1.3 million, respectively. As required by these agreements, the Company committed to spend approximately $15.0 million in the related land development, which primarily includes the construction of fixed assets according to a specific timetable. As of June 30, 2020, the Company has spent $14.9 million on such construction. The Company anticipates that this spending commitment will be met by the end of 2020.

Litigation

Litigation	6 Months Ended
	Jun. 30, 2020
Litigation
Litigation	Note 18. Litigation ​ Momenta/Sandoz Enoxaparin Patent and Antitrust Litigation ​ In September 2011, Momenta Pharmaceuticals, Inc., or Momenta, a Boston based pharmaceutical company, and Sandoz Inc., or Sandoz, the generic division of Novartis, initiated litigation against the Company for alleged patent infringement of two patents related to testing methods for batch release of enoxaparin, which the Company refers to as the “’886 patent” and the “’466 patent.” The lawsuit was filed in the United States District Court for the District of Massachusetts, or the Massachusetts District Court. ​ On September 17, 2015, the Company initiated an antitrust lawsuit by filing a complaint in the California District Court against Momenta and Sandoz, or the Defendants. The Company’s complaint generally asserted that Defendants had engaged in certain types of illegal, monopolistic, and anticompetitive conduct giving rise to various causes of action against them. This lawsuit was subsequently transferred to the Massachusetts District Court. ​ On May 20, 2019, the Company and the Plaintiffs entered into a Settlement Agreement to fully settle the patent litigation and antitrust litigation. The Settlement Agreement was contingent upon the District Court’s granting a Joint Motion to Vacate the Patent Judgment and thereafter, the Plaintiffs’ payment of $59.9 million to the Company. On June 18, 2019, the parties filed a Joint Motion to Vacate the Patent Judgment with the District Court, and on the same day, the District Court granted such motion. Accordingly, on June 19, 2019, the parties filed Joint Stipulations with the District Court to dismiss the patent litigation and the antitrust litigation, each of which is self-executing and effective upon filing pursuant to the Federal Rules of Civil Procedure 41(a)(1)(A)(ii). Furthermore, on June 26, 2019, the Federal Circuit issued an Order and a Mandate dismissing the appeal of the patent litigation. On June 27, 2019, pursuant to the Settlement Agreement, the Plaintiffs paid the Company $59.9 million. The Company is not entitled to future rights or royalties related to this settlement. ​ False Claims Act Litigation ​ In January 2009, the Company filed a qui tam complaint in the U.S. District Court for the Central District of California, or the California District Court, alleging that Aventis Pharma S.A., or Aventis, through its acquisition of a patent through false and misleading statements to the U.S. Patent and Trademark Office, as well as through false and misleading statements to the FDA, overcharged the federal and state governments for its Lovenox ® ​ On May 11, 2017, the Company’s lawsuit against Aventis was dismissed for lack of jurisdiction. On July 14, 2017, Aventis filed an application with the District Court for entitlement to attorneys’ fees and expenses. On November 20, 2017, the District Court issued its order granting Aventis’ application for fees, stating that it would refer the matter to a magistrate judge for a report and recommendation regarding the amount of the award to be made. ​ On February 12, 2019, the District Court approved of the parties’ consent for the Magistrate Judge to conduct all further proceedings in this matter at the district court level, including determining the amount of attorneys’ fees to be awarded and entering a final judgment. The Magistrate Judge held a hearing on the Application on May 8, 2019, and indicated that a written opinion on this Application for Fees and Expenses would be forthcoming. The Magistrate Judge’s written opinion on this Application for Fees and Expenses has not been issued yet. The Company intends to continue to vigorously defend against any imposition of attorneys’ fees and expenses in this case. ​ Epinephrine (0.1 mg/mL) Patent Litigation ​ On June 28, 2018, Belcher Pharmaceuticals, LLC, or Belcher initiated a lawsuit in the United States District Court for the District of Delaware by filing a complaint against IMS for infringement of U.S. Patent No. 9,283,197 (the “197 Patent”) with regard to IMS’s New Drug Application No. 211363, filed under 21 U.S.C. § 355(b)(2) of the Hatch-Waxman Act, for FDA approval to manufacture and sell 0.1 mg/mL epinephrine injections. On July 3, 2019, Parties filed a Joint Stipulation to stay the litigation pending the Court’s ruling on the outcome of Belcher’s trial with Hospira. On August 19, 2019, the judge signed the order staying the litigation pending the Court’s ruling on the outcome of Belcher’s trial with Hospira because it involves the same ‘197 Patent as the Company’s litigation. On March 31, 2020, the Court in Belcher’s trial with Hospira issued its ruling in favor of Hospira and invalidated the ‘197 Patent based on obviousness and the ‘197 Patent is unenforceable due to inequitable conduct, and accordingly, the Court entered Final Judgment in favor of Hospira on April 3, 2020. Belcher filed a notice of appeal on only the inequitable conduct rulings from Final Judgment in favor of Hospira on May 4, 2020, and therefore, the ‘197 Patent is still invalid based on obviousness. On May 21, 2020, the Court entered an Order dismissing, with prejudice, the Company’s patent lawsuit with Belcher. ​ Vasopressin (20 units/mL) Patent Litigation ​ On December 20, 2018, Par Pharmaceutical, Inc., Par Sterile Products, LLC and Endo Par Innovation Company (collectively, “Par”) initiated a patent lawsuit by filing a Complaint against the Company in the United States District Court for the District of Delaware for infringement of U.S. Patent Nos. 9,375,478 (“the ‘478 Patent”), 9,687,526 (“the ‘526 Patent”), 9,744,209 (“the ‘209 Patent”), 9,744,239 (“the ‘239 Patent”), 9,750,785 (“the ‘785 Patent”) and 9,937,223 (“the ‘223 Patent”) (collectively, “Par Patents”) with regard to the Company’s Abbreviated New Drug Application No. 211,857 for FDA approval to manufacture and sell Vasopressin (20 units/ mL). The Company filed its Answer to this Complaint on February 19, 2019. On April 18, 2019, the Court held a scheduling conference and entered a Scheduling Order. ​ On September 27, 2019, the Court entered a Revised Scheduling Order that consolidates the Company’s vasopressin patent lawsuit with two other vasopressin patent lawsuits filed by Par in the same Court, Par v. Amneal Pharmaceuticals GMBH et al., and Par v. American Regent, Inc. (collectively, the “Consolidated Vasopressin Patent Lawsuit”). In the Revised Scheduling Order, trial is still scheduled for January 2021 and the Company’s 30-month FDA stay is maintained at May 21, 2021. On the same day, the Court entered a Protective Order on the Consolidated Vasopressin Patent Lawsuits. On December 9, 2019, the Court entered a Second Revised Scheduling Order to include Fresenius Kabi USA, LCC as part of the Consolidated Vasopressin Patent Lawsuit, with trial still scheduled for January 11, 2021 and the Company’s 30-month FDA stay still maintained at May 21, 2021. On May 21, 2020, the Court entered a Consent Judgment between Par and American Regent, Inc., and thus, American Regent, Inc. is no longer part of the Consolidated Vasopressin Patent Lawsuit. The Company intends to vigorously defend this patent lawsuit. ​ Regadenoson (0.4 mg/5 mL, 0.08 mg/mL) Patent Litigation ​ On February 25, 2020, Astellas US LLC, Astellas Pharma US, Inc., and Gilead Sciences, Inc. (collectively, “Astellas-Gilead”) initiated a patent lawsuit by filing a Complaint in the United States District Court for the District of Delaware against IMS for infringement of U.S. Patent Nos. 8,106,183 (the “‘183 patent”), RE47,301 (the “‘301 patent”), and 8,524,883 (the “‘883 patent”) (collectively, “Astellas-Gilead Patents”) with regard to IMS’s Abbreviated New Drug Application No. 214,252 for FDA approval to manufacture and sell 0.4 mg/5 mL (0.08 mg/mL) intravenous solution of Regadenoson. On March 4, 2020, IMS filed its Answer to the Complaint and its Counterclaims. On March 30, 2020, the Court issued an Order allowing the Company to join the consolidated litigation in which five other generic Regadenoson ANDA filers are currently pending. In the consolidated litigation, trial is currently scheduled for June 14, 2021. The Company’s 30-month FDA stay expires August 10, 2022. The Company intends to vigorously defend this patent lawsuit. ​ Employment Litigation ​ a. Raquel Brenes ​ On September 11, 2019, a former employee, Raquel Brenes, (“Brenes”), initiated an employment litigation against IMS et al. by filing a Complaint having individual and class action claims for alleged violations of various California labor laws pertaining to wage and hour, and other state laws. This Complaint was filed in the Superior Court of California, Los Angeles County. On September 18, 2019, Brenes filed a First Amended Complaint maintaining the individual and class action claims. On January 21, 2020, Brenes filed a Second Amended Complaint that alleges only Private Attorney General Act, or PAGA, claims and omitted the individual and class action claims. On February 24, 2020, IMS filed an Answer to the Second Amended Complaint. On February 14, 2020, Brenes filed another Complaint against IMS in the Superior Court of California alleging various individual claims relating to disability discrimination and retaliation. The parties have agreed to reschedule the August 21, 2020 mediation to a later date due to the recent change in our Company’s outside labor counsel. The Company intends to vigorously defend this employment litigation. ​ b. Robert Navarrette ​ On April 7, 2020, a former employee, Robert Navarrette (“Navarrette”), filed a PAGA lawsuit against IMS and Amphastar Pharmaceuticals, Inc. in the Superior Court of California, Los Angeles County. In this PAGA lawsuit, Navarrette alleges various wage and hour claims. Navarrette has agreed to mediate this PAGA lawsuit, along with Brenes’ PAGA lawsuit. The parties are currently evaluating mediators and their availability for this mediation. The Company intends to vigorously defend this employment litigation. ​ c. Priscilla Ramirez ​ On April 10, 2020, ex-employee Priscilla Ramirez provided written notice to Amphastar Pharmaceuticals, Inc. that she intends to file a PAGA lawsuit for alleged violations of various California labor laws pertaining to wage and hour. On May 29, 2020, Ramirez filed this PAGA lawsuit against the Company. On August 4, 2020, Ramirez served this PAGA lawsuit on our Company. The Company intends to vigorously defend this lawsuit. ​ Other Litigation ​ The Company is also subject to various other claims and lawsuits from time to time arising in the ordinary course of business. ​ The Company records a provision for contingent losses when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. In the opinion of management, the ultimate resolution of any such matters is not expected to have a material adverse effect on its financial position, results of operations, or cash flows; however, the results of litigation and claims are inherently unpredictable and the Company’s view of these matters may change in the future. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation ​ The unaudited condensed consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with United States generally accepted accounting principles, or GAAP. All intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company. ​ The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Nanjing Letop Biological Technology Co., Ltd., or Letop, (5) Nanjing Hanxin Pharmaceutical Technology Co., Ltd., or Hanxin, (6) Nanjing Hanxin Biomedical Testing Service Co., Ltd., or Hanxin Biomedical, (7) Nanjing Baixin Trading Co. Ltd., or Baixin, (8) Amphastar France Pharmaceuticals, S.A.S., or AFP, (9) Amphastar UK Ltd., or AUK, and (10) International Medication Systems (UK) Limited, or IMS UK. ​ In July 2018, the Company’s Chinese subsidiary, ANP, completed a private placement of its common equity interest to accredited investors for aggregate gross proceeds of approximately $57 million, a portion of which was received in 2019. The Company has retained approximately 58% of the equity interest in ANP following the private placement and continues to consolidate the financial results of ANP with the Company’s results of operations. ANP’s net income after July 2, 2018, was attributed to the Company in accordance with the Company’s equity interest of approximately 58% in ANP.
COVID-19 Pandemic	COVID-19 Pandemic ​ The Company is subject to risks and uncertainties as a result of the novel coronavirus pandemic, or COVID-19. The extent of the impact of the COVID-19 pandemic on the Company’s business is highly uncertain and difficult to predict, as the response to the pandemic is in its initial stages and information is rapidly evolving. The Company considered the impact of COVID-19 on the assumptions and estimates used to determine the results reported and asset valuations as of June 30, 2020. ​ In March 2020, the World Health Organization declared the outbreak of a novel coronavirus, or COVID-19, as a pandemic, which continues to spread throughout the world, including locations where the Company operates, such as the United States, China and France. The Company has been actively monitoring the COVID-19 pandemic and its impact globally. In late January 2020, China implemented extensive curfews and travel restrictions to control the outbreak, and started easing these restrictions in March. Our business operations in China experienced a temporary disruption but resumed full operation in February 2020. In March 2020, France also implemented a stay-at-home order limiting movement and restricting travel, however, the Company was deemed to be an essential business and was not impacted by the restrictions. In March 2020, the Governors of the States of California and Massachusetts declared a health emergency and issued orders to close all nonessential business; as a specialty pharmaceutical company, the Company was deemed to be an essential businesses. In June 2020, some but not all of the restrictions were lifted in China, France, and states where the Company operates, and most businesses were allowed to reopen. All of the Company’s production facilities continued to operate during the quarter as they had prior to the COVID-19 pandemic with very little change, other than for enhanced safety measures intended to prevent the spread of the virus. ​ It is not possible at this time to estimate the complete impact that COVID-19 could have on the Company’s business, as the impact will depend on future developments, which are highly uncertain and cannot be predicted. Infections may resurge or become more widespread and the limitation on the Company’s ability to travel and timely sell and distribute its products, as well as any closures or supply disruptions, may be extended for longer periods of time, all of which would have a negative impact on the Company’s business, financial condition and operating results. The Company will continue to monitor the impact of COVID-19 on all aspects of its business.
Use of Estimates	Use of Estimates ​ The preparation of condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for credit losses, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to their net realizable values, impairment of long-lived and intangible assets and goodwill, workers’ compensation liabilities, litigation reserves, stock price volatilities for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions.
Foreign Currency	Foreign Currency ​ The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary, ANP, and its U.K. subsidiary, AUK, is the USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s condensed consolidated statements of operations. ​ The Company’s French subsidiary, AFP, maintains its book of record in euros. ANP’s Chinese subsidiaries maintain their books of record in Chinese yuan. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. These books of record are translated into USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other accumulated comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature for the three months ended June 30, 2020, was $0.7 million gain and an immaterial loss for the six months ended June 30, 2020. For the three and six months ended June 30, 2019, the unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature was $0.4 million gain and $0.2 million loss, respectively. ​
Comprehensive Income (Loss)	Comprehensive Income (Loss) ​ For the three and six months ended June 30, 2020 and 2019, the Company included its foreign currency translation gain or loss as part of its comprehensive income (loss). There was no material income tax (benefit) expense allocated to other comprehensive income (loss) for the three and six months ended June 30, 2020 and 2019.
Advertising Expense	Advertising Expense ​ In connection with the launch of Primatene ®
Restricted Cash	Restricted Cash ​ Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of June 30, 2020 and December 31, 2019, the restricted cash balance was $1.9 million.
Restricted Short-Term Investments	Restricted Short-Term Investments ​ Restricted short-term investments consist of certificates of deposit that are collateral for standby letter of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months. As of June 30, 2020 and December 31, 2019, the balance of restricted short-term investments was $2.2 million and $2.3 million, respectively.
Financial Instruments	Financial Instruments ​ The carrying amounts of cash and cash equivalents, short-term investments, restricted cash and short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. The majority of the Company’s long-term obligations consist of variable rate debt, and their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. The Company at times enters into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates without the exchange of the underlying notional debt amounts. Such interest rate swap contracts are recorded at their fair values.
Cash and Cash Equivalents	Cash and Cash Equivalents ​ Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments purchased with original maturities of three months or less.
Short-Term Investments	Short-Term Investments ​ Short-term investments as of June 30, 2020 and December 31, 2019 consisted of certificates of deposit and investment grade corporate bonds with original expiration dates within 12 months.
Deferred Income Taxes	Deferred Income Taxes ​ The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ In December 2019, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update, or ASU, No. 2019-12 Simplifying the Accounting for Income Taxes (Topic 740) ​ In April 2020, the FASB issued ASU No. 2020-04 Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting,

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue Recognition
Schedule of chargeback and rebates provision analysis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 21,644 $ 22,423 ​ Provision for chargebacks and rebates ​ 69,424 ​ 58,001 ​ Credits and payments issued to third parties ​ (72,625) ​ (61,704) ​ Ending balance ​ $ 18,443 ​ $ 18,720 ​
Schedule of product return liability analysis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 10,339 $ 8,030 ​ Provision for product returns ​ 6,208 ​ 3,654 ​ Credits issued to third parties ​ (3,989) ​ (2,243) ​ Ending balance ​ $ 12,558 ​ $ 9,441 ​

(Loss) Income per Share Attri_2

(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders (Tables)	6 Months Ended
	Jun. 30, 2020
(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders
Schedule of basic and diluted net income (loss) per share calculation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands, except per share data) ​ Basic and dilutive numerator: ​ ​ ​ ​ Net (loss) income attributable to Amphastar Pharmaceuticals, Inc. ​ $ (192) ​ $ 47,787 ​ $ 3,757 ​ $ 48,655 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares outstanding — basic ​ 46,753 ​ 47,107 ​ 46,581 ​ 46,925 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Incremental shares from equity awards ​ — ​ 2,787 ​ 1,877 ​ 3,230 ​ Weighted-average shares outstanding — diluted ​ 46,753 ​ 49,894 ​ 48,458 ​ 50,155 ​ Net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders — basic ​ $ (0.00) ​ $ 1.01 ​ $ 0.08 ​ $ 1.04 ​ Net (loss) income per share attributable to Amphastar Pharmaceuticals, Inc. shareholders — diluted ​ $ (0.00) ​ $ 0.96 ​ $ 0.08 ​ $ 0.97 ​

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting
Schedule of financial information by reporting segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Net revenues: ​ ​ ​ ​ Finished pharmaceutical products ​ $ 80,935 ​ $ 73,735 ​ $ 162,233 ​ $ 148,274 ​ API ​ 4,871 ​ 5,312 ​ 8,261 ​ ​ 10,563 ​ Total net revenues ​ 85,806 ​ 79,047 ​ 170,494 ​ 158,837 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross profit: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finished pharmaceutical products ​ 35,437 ​ 34,540 ​ 74,247 ​ 66,852 ​ API ​ (2,260) ​ (2,153) ​ (4,247) ​ ​ (3,562) ​ Total gross profit ​ 33,177 ​ 32,387 ​ 70,000 ​ 63,290 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ 36,099 ​ 31,414 ​ 65,442 ​ 65,489 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Loss) income from operations ​ (2,922) ​ 973 ​ 4,558 ​ (2,199) ​ Non-operating expense ​ 1,418 ​ 60,120 ​ (257) ​ 59,659 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (Loss) income before income taxes ​ $ (1,504) ​ $ 61,093 ​ $ 4,301 ​ $ 57,460 ​
Schedule of net revenues in the finished pharmaceutical products segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Finished pharmaceutical products net revenues: ​ ​ ​ ​ ​ Primatene ® ​ $ 12,468 ​ $ 2,512 ​ $ 25,345 ​ $ 5,409 ​ Phytonadione ​ 10,689 ​ 12,441 ​ 21,718 ​ 22,561 ​ Enoxaparin ​ ​ 10,218 ​ ​ 9,838 ​ ​ 19,386 ​ ​ 24,322 ​ Lidocaine ​ ​ 7,608 ​ ​ 10,082 ​ ​ 18,265 ​ ​ 22,061 ​ Naloxone ​ ​ 8,723 ​ ​ 7,833 ​ ​ 17,598 ​ ​ 15,197 ​ Epinephrine ​ ​ 6,957 ​ ​ 3,139 ​ ​ 10,947 ​ ​ 5,818 ​ Other finished pharmaceutical products ​ 24,272 ​ 27,890 ​ 48,974 ​ 52,906 ​ Total finished pharmaceutical products net revenues ​ $ 80,935 ​ $ 73,735 ​ $ 162,233 ​ $ 148,274 ​
Schedule of depreciation and amortization expense by reporting segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ (in thousands) ​ Depreciation and amortization expense ​ ​ ​ ​ Finished pharmaceutical products ​ $ 1,453 ​ $ 1,371 ​ $ 2,917 ​ $ 2,721 ​ API ​ 575 ​ 290 ​ 1,157 ​ ​ 575 ​ Total depreciation and amortization expense ​ $ 2,028 ​ $ 1,661 ​ $ 4,074 ​ $ 3,296 ​
Schedule of net revenues and carrying values of long-lived assets by geographic region	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net Revenue ​ Long-Lived Assets ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ June 30, ​ June 30, ​ December 31, ​ ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ (in thousands) United States $ 81,898 $ 74,781 $ 162,963 $ 151,238 $ 106,301 $ 108,399 ​ China ​ 295 ​ 984 ​ 523 ​ 984 ​ 81,951 ​ 79,846 ​ France ​ 3,613 ​ 3,282 ​ 7,008 ​ ​ 6,615 ​ 49,984 ​ 45,611 ​ Total ​ $ 85,806 ​ $ 79,047 ​ $ 170,494 ​ $ 158,837 ​ $ 238,236 ​ $ 233,856 ​

Customer and Supplier Concent_2

Customer and Supplier Concentration (Tables)	6 Months Ended
	Jun. 30, 2020
Customer and Supplier Concentration
Schedule of accounts receivable and net revenues by major customer	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ % of Total Accounts ​ % of Net ​ ​ Receivable ​ Revenue ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ December 31, ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 2020 2019 AmerisourceBergen 9 % 13 % 23 % 25 % 23 % 23 % McKesson 22 % 34 % 23 % 25 % 23 % 27 % Cardinal Health 22 % 17 % 19 % 21 % 19 % 23 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Measurements
Schedule of financial assets and liabilities measured on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) Cash equivalents - money market ​ $ 62,525 ​ $ 62,525 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 1,865 ​ ​ 1,865 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 9,079 ​ ​ — ​ ​ 9,079 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,200 ​ — ​ 2,200 ​ — ​ Corporate bonds ​ ​ 2,010 ​ ​ — ​ ​ 2,010 ​ ​ — ​ Fair value measurement as of June 30, 2020 ​ $ 77,679 ​ $ 64,390 ​ $ 13,289 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market ​ $ 29,521 ​ $ 29,521 ​ $ — ​ $ — ​ Restricted cash - money market ​ ​ 1,865 ​ ​ 1,865 ​ ​ — ​ ​ — ​ Short-term investments - certificates of deposit ​ ​ 8,867 ​ ​ — ​ ​ 8,867 ​ ​ — ​ Restricted short-term investments - certificates of deposit ​ 2,290 ​ — ​ 2,290 ​ — ​ Corporate bonds ​ ​ 2,789 ​ ​ — ​ ​ 2,789 ​ ​ — ​ Fair value measurement as of December 31, 2019 ​ $ 45,332 ​ $ 31,386 ​ $ 13,946 ​ $ — ​

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2020
Investments
Schedule of securities classified as held-to-maturity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Cost Gains Losses Value ​ ​ (in thousands) Corporate bonds ​ $ 2,005 ​ $ 5 ​ $ — ​ $ 2,010 Total investments as of June 30, 2020 ​ $ 2,005 ​ $ 5 ​ $ — ​ $ 2,010 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate bonds ​ $ 2,790 ​ $ — ​ $ (1) ​ $ 2,789 Total investments as of December 31, 2019 ​ $ 2,790 ​ $ — ​ $ (1) ​ $ 2,789

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets
Schedule of weighted-average life, original cost, accumulated amortization and net book value by major class	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 8,625 ​ $ 3,378 ​ $ 5,247 ​ Patents 12 ​ 486 ​ ​ 276 ​ 210 ​ Land-use rights 39 ​ 2,540 ​ ​ 584 ​ 1,956 ​ Subtotal 12 ​ 11,651 ​ 4,238 ​ 7,413 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,633 ​ — ​ 3,633 ​ Subtotal * ​ 32,858 ​ — ​ 32,858 ​ As of June 30, 2020 * ​ $ 44,509 ​ $ 4,238 ​ $ 40,271 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ ​ ​ ​ Life (Years) Original Cost Amortization Net Book Value ​ ​ (in thousands) Definite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ IMS (UK) international product rights ​ 10 ​ $ 9,226 ​ $ 3,152 ​ $ 6,074 ​ Patents 12 ​ 486 ​ 255 ​ 231 ​ Land-use rights 39 ​ 2,540 ​ 551 ​ 1,989 ​ Other intangible assets 4 ​ 69 ​ 69 ​ — ​ Subtotal 12 ​ 12,321 ​ 4,027 ​ 8,294 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trademark * ​ 29,225 ​ — ​ 29,225 ​ Goodwill - Finished pharmaceutical products * ​ 3,634 ​ — ​ 3,634 ​ Subtotal * ​ 32,859 ​ — ​ 32,859 ​ As of December 31, 2019 * ​ $ 45,180 ​ $ 4,027 ​ $ 41,153 ​ * Intangible assets with indefinite lives have an indeterminable average life.
Schedule of changes in carrying amounts of goodwill	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Beginning balance $ 3,634 $ 3,951 ​ Currency translation ​ (1) ​ (317) ​ Ending balance ​ $ 3,633 ​ $ 3,634 ​

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2020
Inventories
Schedule of inventories	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Raw materials and supplies $ 50,657 $ 59,233 ​ Work in process ​ 39,169 ​ 35,548 ​ Finished goods ​ 14,900 ​ 15,720 ​ Total inventories ​ $ 104,726 ​ $ 110,501 ​

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	6 Months Ended
	Jun. 30, 2020
Property, Plant, and Equipment
Schedule of property, plant, and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Buildings $ 119,648 $ 117,928 ​ Leasehold improvements ​ 29,510 ​ 29,531 ​ Land ​ 7,604 ​ 7,603 ​ Machinery and equipment ​ 174,308 ​ 164,802 ​ Furniture, fixtures, and automobiles ​ 24,787 ​ 22,043 ​ Construction in progress ​ 55,832 ​ 56,354 ​ Total property, plant, and equipment ​ 411,689 ​ 398,261 ​ Less accumulated depreciation ​ (173,453) ​ (164,405) ​ Total property, plant, and equipment, net ​ $ 238,236 ​ $ 233,856 ​

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Accounts Payable and Accrued Liabilities.
Schedule of accounts payable and accrued liabilities	​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 ​ (in thousands) Accrued customer fees and rebates $ 9,049 ​ $ 9,633 Accrued payroll and related benefits ​ 23,134 ​ ​ 21,872 Accrued product returns, current portion ​ 8,326 ​ ​ 7,126 Accrued loss on firm purchase commitments ​ 5,520 ​ ​ 3,352 Other accrued liabilities ​ 7,648 ​ ​ 10,007 Total accrued liabilities 53,677 ​ 51,990 Accounts payable 21,708 ​ 25,061 Total accounts payable and accrued liabilities $ 75,385 ​ $ 77,051

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt
Schedule of debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ (in thousands) Loans with East West Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due December 2020 ​ $ — ​ $ — ​ Mortgage payable due February 2021 ​ ​ 3,354 ​ ​ 3,401 ​ Equipment loan due June 2021 ​ ​ 1,224 ​ ​ 1,837 ​ Equipment loan due December 2022 ​ ​ 5,000 ​ ​ 6,000 ​ Equipment loan due February 2024 ​ ​ 6,084 ​ ​ 3,570 ​ Mortgage payable due October 2026 ​ ​ 3,367 ​ ​ 3,400 ​ Mortgage payable due June 2027 ​ ​ 8,586 ​ ​ 8,659 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans with Cathay Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due May 2022 ​ — ​ — ​ Acquisition loan due June 2024 ​ 9,833 ​ 10,928 ​ Mortgage payable due August 2027 ​ 7,361 ​ 7,452 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans with Seine-Normandie Water Agency ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ French government loan due June 2020 ​ ​ — ​ ​ 28 ​ French government loan due July 2021 ​ ​ 118 ​ ​ 114 ​ French government loans due December 2026 ​ ​ 380 ​ ​ 374 ​ ​ ​ ​ ​ ​ ​ ​ ​ Loan with China Everbright Bank ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Line of credit facility due June 2021 ​ ​ 707 ​ ​ — ​ ​ ​ ​ ​ ​ ​ ​ ​ Payment Obligation to Merck ​ — ​ 561 ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment under Finance Leases ​ 683 ​ 811 ​ Total debt ​ 46,697 ​ 47,135 ​ Less current portion of long-term debt ​ 12,075 ​ 7,741 ​ Long-term debt, net of current portion ​ $ 34,622 ​ $ 39,394 ​

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2020
Income Taxes
Summary of provision (benefit) for income taxes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2020 2019 2020 2019 ​ ​ (in thousands) (Loss) income before taxes ​ $ (1,504) ​ $ 61,093 ​ $ 4,301 ​ $ 57,460 ​ Income tax (benefit) provision ​ ​ (75) ​ 14,173 ​ ​ 2,205 ​ 12,694 ​ Net (loss) income ​ $ (1,429) ​ $ 46,920 ​ $ 2,096 ​ $ 44,766 ​ Income tax (benefit) provision as a percentage of (loss) income before income taxes ​ ​ 5.0 % 23.2 % ​ 51.3 % 22.1 %

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2020
Stockholders' Equity
Schedule of key assumptions to determine fair value of options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 2019 2020 2019 ​ Average volatility 44.0 % 43.4 % 43.1 % 42.5 % ​ Risk-free interest rate 0.5 % 2.0 % 0.8 % 2.4 % ​ Weighted-average expected life in years 4.9 ​ 5.0 ​ 5.7 ​ 5.7 ​ ​ Dividend yield rate — % — % — % — % ​
Schedule of the summary of option activity under all plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ Remaining ​ Aggregate ​ ​ ​ ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term (Years) ​ Value (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Outstanding as of December 31, 2019 9,763,485 $ 15.26 ​ ​ Options granted 1,789,254 ​ 13.52 ​ ​ ​ ​ ​ ​ Options exercised (1,473,323) ​ 14.22 ​ ​ ​ ​ ​ ​ Options cancelled (84,203) ​ 16.53 ​ ​ ​ ​ ​ ​ Options expired (1,108,177) ​ 16.45 ​ ​ ​ ​ ​ ​ Outstanding as of June 30, 2020 8,887,036 ​ $ 14.92 5.65 ​ $ 66,980 ​ Exercisable as of June 30, 2020 6,029,545 ​ $ 14.31 4.41 ​ $ 49,123 ​ (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the estimated fair value of the Company’s common stock for those awards that have an exercise price below the estimated fair value at June 30, 2020.
Schedule of information relating to options grants	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2020 2019 2020 2019 ​ ​ (in thousands, except per share data) Weighted-average grant date fair value per option share ​ $ 7.15 ​ $ 8.17 ​ $ 5.48 ​ $ 8.46 ​ Intrinsic value of options exercised ​ 6,486 ​ 452 ​ 6,974 ​ 5,822 ​ Cash received from options exercised ​ 19,088 ​ 1,108 ​ 20,339 ​ 5,047 ​ Total fair value of the options vested during the year ​ 2,411 ​ 388 ​ 9,844 ​ 7,502 ​
Schedule of the summary of nonvested options status	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ Options ​ Fair Value Non-vested as of December 31, 2019 ​ 2,747,133 ​ $ 6.99 ​ Options granted 1,789,254 ​ 5.48 ​ Options vested (1,594,693) ​ 6.17 ​ Options forfeited (84,203) ​ 7.13 ​ Non-vested as of June 30, 2020 2,857,491 ​ 6.50 ​
Schedule of information relating to RSU grants and deliveries	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair Market ​ ​ ​ ​ Value of RSUs ​ ​ ​ ​ Issued ​ ​ Total RSUs ​ as ​ Issued Compensation (1) ​ ​ ​ ​ (in thousands) RSUs outstanding at December 31, 2019 1,099,496 ​ ​ ​ ​ RSUs granted 727,746 ​ $ 9,811 ​ RSUs forfeited (35,792) ​ ​ ​ ​ RSUs vested (2) (614,971) ​ ​ ​ ​ RSUs outstanding at June 30, 2020 1,176,479 ​ ​ ​ ​ (1) The total fair market value is derived from the number of RSUs granted times the stock price on the date of grant. (2) Of the vested RSUs, 235,053 shares of common stock were surrendered to fulfill tax withholding obligations.
Schedule of recorded share-based compensation expense under all plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ ​ 2020 ​ 2019 ​ 2020 2019 ​ ​ (in thousands) Cost of revenues $ 970 $ 959 $ 2,329 $ 2,238 ​ Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Selling, distribution, and marketing ​ 123 ​ 95 ​ 230 ​ 189 ​ General and administrative ​ 5,052 ​ 2,648 ​ 8,271 ​ 5,439 ​ Research and development ​ 368 ​ 330 ​ 965 ​ 840 ​ Total share-based compensation ​ $ 6,513 ​ $ 4,032 ​ $ 11,795 ​ $ 8,706 ​

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Jul. 02, 2018	Jul. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2019
Proceeds from private placement					$ 18,298
Gains and (losses) of intercompany foreign currency transactions			$ 700	$ 400	(200)
Restricted cash			1,865			$ 1,865
Certificates of deposit			$ 2,200			$ 2,300
ANP
Proceeds from private placement		$ 57,000
Equity interest retained post private placement	58.00%
Finished Pharmaceutical Products | Primatene Mist
Advertising cost				$ 1,400	$ 2,400

Revenue Recognition (Analysis o

Revenue Recognition (Analysis of the Chargeback Provision) (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Beginning balance	$ 21,644	$ 22,423	$ 22,423
Provision for chargebacks and rebates	69,424	58,001
Credits and payments issued to third parties	(72,625)	(61,704)
Ending balance	18,443	$ 18,720	21,644
Accounts Receivable, Net
Provision for chargebacks and rebates	14,100		15,400
Accounts Payable and Accrued Liabilities
Provision for chargebacks and rebates	$ 4,300		$ 6,200

Revenue Recognition (Analysis_2

Revenue Recognition (Analysis of Product Return Liability) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Aggregate product return rate	1.30%	1.50%
Return accrual included in accounts payable and accrued liabilities	$ 8,326		$ 7,126
Return accrual included in other long-term liabilities	4,300		$ 3,200
Product returns
Beginning balance	10,339	$ 8,030
Provision for product returns	6,208	3,654
Credits issued to third parties	(3,989)	(2,243)
Ending balance	$ 12,558	$ 9,441

(Loss) Income per Share Attri_3

(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders (Narrative) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Exercise Price of Excluded Securities			$ 20.84
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	8,887,036	783,001	1,928,773	762,937
Antidilutive Securities Excluded from Computation of Earnings Per Share, Exercise Price of Excluded Securities		$ 21.98		$ 22
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	1,176,479
Employee Stock Purchase Plan (ESPP)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	60,386

(Loss) Income per Share Attri_4

(Loss) Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Shareholders (Calculation of Basic and Diluted Net Income (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic and dilutive numerator:
Net Income (Loss) Attributable to Parent	$ (192)	$ 3,949	$ 47,787	$ 868	$ 3,757	$ 48,655
Denominator:
Weighted-average shares outstanding-basic	46,753		47,107		46,581	46,925
Net effect of dilutive securities:
Incremental shares from equity awards			2,787		1,877	3,230
Weighted-average shares outstanding - diluted	46,753		49,894		48,458	50,155
Net income (loss) per share - basic	$ 0		$ 1.01		$ 0.08	$ 1.04
Net income (loss) per share - diluted	$ 0		$ 0.96		$ 0.08	$ 0.97

Segment Reporting (Selected Fin

Segment Reporting (Selected Financial Information by Reporting Segment) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)segment	Jun. 30, 2019USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			2
Net revenues:
Net Revenue	$ 85,806	$ 79,047	$ 170,494	$ 158,837
Gross Profit:
Gross Profit	33,177	32,387	70,000	63,290
Operating expenses	36,099	31,414	65,442	65,489
Income (loss) from operations	(2,922)	973	4,558	(2,199)
Non-operating income (expenses)	1,418	60,120	(257)	59,659
Income (loss) before income taxes	(1,504)	61,093	4,301	57,460
Finished Pharmaceutical Products
Net revenues:
Net Revenue	80,935	73,735	162,233	148,274
Gross Profit:
Gross Profit	35,437	34,540	74,247	66,852
API
Net revenues:
Net Revenue	4,871	5,312	8,261	10,563
Gross Profit:
Gross Profit	$ (2,260)	$ (2,153)	$ (4,247)	$ (3,562)

Segment Reporting (Summary of N

Segment Reporting (Summary of Net Revenues by Product Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	$ 85,806	$ 79,047	$ 170,494	$ 158,837
Finished Pharmaceutical Products
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	80,935	73,735	162,233	148,274
Finished Pharmaceutical Products | Enoxaparin
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	10,218	9,838	19,386	24,322
Finished Pharmaceutical Products | Lidocaine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	7,608	10,082	18,265	22,061
Finished Pharmaceutical Products | Phytonadione
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	10,689	12,441	21,718	22,561
Finished Pharmaceutical Products | Naloxone
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	8,723	7,833	17,598	15,197
Finished Pharmaceutical Products | Epinephrine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	6,957	3,139	10,947	5,818
Finished Pharmaceutical Products | Primatene Mist
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	12,468	2,512	25,345	5,409
Finished Pharmaceutical Products | Other Finished Pharmaceutical Products
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Net Revenue	$ 24,272	$ 27,890	$ 48,974	$ 52,906

Segment Reporting (Depreciation

Segment Reporting (Depreciation and Amortization Expense by Reporting Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 2,028	$ 1,661	$ 4,074	$ 3,296
Finished Pharmaceutical Products
Segment Reporting Information [Line Items]
Depreciation and amortization expense	1,453	1,371	2,917	2,721
API
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 575	$ 290	$ 1,157	$ 575

Segment Reporting (Summary of R

Segment Reporting (Summary of Revenues and Long-Lived Assets by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Revenue	$ 85,806	$ 79,047	$ 170,494	$ 158,837
Long-Lived Assets	238,236		238,236		$ 233,856
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Revenue	81,898	74,781	162,963	151,238
Long-Lived Assets	106,301		106,301		108,399
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Revenue	295	984	523	984
Long-Lived Assets	81,951		81,951		79,846
FRANCE
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Revenue	3,613	$ 3,282	7,008	$ 6,615
Long-Lived Assets	$ 49,984		$ 49,984		$ 45,611

Customer and Supplier Concent_3

Customer and Supplier Concentration (Details) - Customer Concentration Risk [Member] - item	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue, Major Customer [Line Items]
Number of major customers that are wholesale distributors			3
Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Number of major customers			3		3
Net Revenues
Revenue, Major Customer [Line Items]
Number of major customers	3	3	3	3
AmerisourceBergen | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers			9.00%		13.00%
AmerisourceBergen | Net Revenues
Revenue, Major Customer [Line Items]
Major Customers	23.00%	25.00%	23.00%	23.00%
Cardinal Health | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers			22.00%		17.00%
Cardinal Health | Net Revenues
Revenue, Major Customer [Line Items]
Major Customers	19.00%	21.00%	19.00%	23.00%
McKesson | Accounts Receivable, Net
Revenue, Major Customer [Line Items]
Major Customers			22.00%		34.00%
McKesson | Net Revenues
Revenue, Major Customer [Line Items]
Major Customers	23.00%	25.00%	23.00%	27.00%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Values of the Company's Financial Assets and Liabilities) (Details) - Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	$ 77,679	$ 45,332
Corporate bonds
Corporate bonds	2,010	2,789
Money market
Cash equivalents:
Cash equivalents	62,525	29,521
Restricted cash:
Restricted cash	1,865	1,865
Certificates of deposit
Short-term investments:
Short-term investments	9,079	8,867
Restricted short-term investments:
Restricted short-term investments	2,200	2,290
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	64,390	31,386
Level 1 | Money market
Cash equivalents:
Cash equivalents	62,525	29,521
Restricted cash:
Restricted cash	1,865	1,865
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement	13,289	13,946
Corporate bonds
Corporate bonds	2,010	2,789
Level 2 | Certificates of deposit
Short-term investments:
Short-term investments	9,079	8,867
Restricted short-term investments:
Restricted short-term investments	$ 2,200	$ 2,290

Investments (Held-to_Maturity)

Investments (Held-to_Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 2,005	$ 2,790
Gross Unrealized Gains	5
Gross Unrealized Losses		(1)
Fair Value	2,010	2,789
Corporate Bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,005	2,790
Gross Unrealized Gains	5
Gross Unrealized Losses		(1)
Fair Value	$ 2,010	$ 2,789

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Definite-lived intangible assets
Weighted-Average Life (Years)	12 years	12 years
Finite-Lived Intangible Assets, Gross	$ 11,651	$ 12,321
Accumulated Amortization	4,238	4,027
Finite-Lived Intangible Assets, Net	7,413	8,294
Indefinite-lived intangible assets
Goodwill recognized	3,633	3,634	$ 3,951
Subtotal, Original Cost	32,858	32,859
Subtotal, Net Book Value	32,858	32,859
Balance, Original Cost	44,509	45,180
Balance, Net Book Value	40,271	41,153
Finished Pharmaceutical Products
Indefinite-lived intangible assets
Goodwill recognized	3,633	3,634
Trademarks
Indefinite-lived intangible assets
Indefinite-lived intangible assets	$ 29,225	$ 29,225
Patents
Definite-lived intangible assets
Weighted-Average Life (Years)	12 years	12 years
Finite-Lived Intangible Assets, Gross	$ 486	$ 486
Accumulated Amortization	276	255
Finite-Lived Intangible Assets, Net	$ 210	$ 231
Land-use rights
Definite-lived intangible assets
Weighted-Average Life (Years)	39 years	39 years
Finite-Lived Intangible Assets, Gross	$ 2,540	$ 2,540
Accumulated Amortization	584	551
Finite-Lived Intangible Assets, Net	$ 1,956	$ 1,989
Other intangible assets
Definite-lived intangible assets
Weighted-Average Life (Years)		4 years
Finite-Lived Intangible Assets, Gross		$ 69
Accumulated Amortization		$ 69
International Medication Systems (UK) Limited | Acquired international product rights
Definite-lived intangible assets
Weighted-Average Life (Years)	10 years	10 years
Finite-Lived Intangible Assets, Gross	$ 8,625	$ 9,226
Accumulated Amortization	3,378	3,152
Finite-Lived Intangible Assets, Net	$ 5,247	$ 6,074

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Summary of Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Goodwill and Intangible Assets
Beginning balance	$ 3,634	$ 3,951
Currency translation and other adjustments	(1)	(317)
Ending balance	$ 3,633	$ 3,634

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Raw materials and supplies	$ 50,657		$ 50,657		$ 59,233
Work in process	39,169		39,169		35,548
Finished goods	14,900		14,900		15,720
Total inventory, net	104,726		104,726		$ 110,501
Inventory adjustment to reflect net realizable value	$ 8,100		$ 10,200
ANP | Crude Heparin
Inventory adjustment to reflect net realizable value		$ 2,500		$ 5,700

Property, Plant, and Equipmen_2

Property, Plant, and Equipment (Summary of Property, Plant, and Equipment) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 411,689	$ 398,261
Less accumulated depreciation and amortization	(173,453)	(164,405)
Total property, plant, and equipment, net	238,236	233,856
Buildings
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	119,648	117,928
Leasehold improvement
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	29,510	29,531
Land
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	7,604	7,603
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	174,308	164,802
Furniture, fixtures, and automobiles
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	24,787	22,043
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 55,832	$ 56,354

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts Payable and Accrued Liabilities.
Accrued customer fees and rebates	$ 9,049	$ 9,633
Accrued payroll and related benefits	23,134	21,872
Accrued product returns, current portion	8,326	7,126
Accrued loss on firm purchase commitments	5,520	3,352
Other accrued liabilities	7,648	10,007
Total accrued liabilities	53,677	51,990
Accounts payable	21,708	25,061
Total accounts payable and accrued liabilities	$ 75,385	$ 77,051

Debt (Schedule of Debt) (Detail

Debt (Schedule of Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument
Equipment under Finance Leases	$ 683	$ 811
Total debt	46,697	47,135
Less current portion of long-term debt and finance leases	12,075	7,741
Long-term debt and finance leases, net of current portion	34,622	39,394
Mortgage Payable - Due February 2021 | East West Bank
Debt Instrument
Long Term Debt	3,354	3,401
Equipment Loan - Due June 2021 | East West Bank
Debt Instrument
Long Term Debt	1,224	1,837
Equipment Loan - Due December 2022 | East West Bank
Debt Instrument
Long Term Debt	5,000	6,000
Equipment Loan - Due February 2024 | East West Bank
Debt Instrument
Long Term Debt	6,084	3,570
Mortgage Payable - Due October 2026 | East West Bank
Debt Instrument
Long Term Debt	3,367	3,400
Mortgage Payable - Due June 2027 | East West Bank
Debt Instrument
Long Term Debt	8,586	8,659
Mortgage Payable - Due August 2027 | Cathay Bank
Debt Instrument
Long Term Debt	7,361	7,452
Acquisition Loan - Due June 2024 | Cathay Bank
Debt Instrument
Long Term Debt	9,833	10,928
Line of credit - Due June 2021 | China Everbright Bank
Debt Instrument
Long Term Debt	707
French Government Loan - Due June 2020 | Seine-Normandie Water Agency
Debt Instrument
Long Term Debt		28
French Government Loan - Due July 2021 | Seine-Normandie Water Agency
Debt Instrument
Long Term Debt	118	114
French Government Loan 4 - Due December 2026 | Seine-Normandie Water Agency
Debt Instrument
Long Term Debt	$ 380	374
Payment Obligation To Merck
Debt Instrument
Long Term Debt		$ 561

Debt (Narrative) (Details)

Debt (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Debt
Proceeds from borrowing under lines of credit		$ 705
East West Bank
Debt
Interest rate swap, fair value		1,200	$ 400
Line of Credit Facility - Due May 2022 | Cathay Bank
Debt
Line of Credit Facility, Maximum Borrowing Capacity		20,000
Line of Credit outstanding		$ 0
Line of Credit Facility - Due May 2022 | Cathay Bank | Prime Rate
Debt
Debt Instrument, Interest Rate, Stated Percentage		3.75%
Line of credit - Due June 2021 | China Everbright Bank
Debt
Debt Instrument, Interest Rate, Stated Percentage		4.05%
Line of Credit Facility, Maximum Borrowing Capacity		$ 700
Line of Credit outstanding		700
Credit Agreement - Expires March 2023 | China Merchant Bank
Debt
Line of Credit Facility, Maximum Borrowing Capacity	$ 14,000
Line of Credit outstanding		$ 0
Draw down period	36 months

Income Taxes (Summary of Income

Income Taxes (Summary of Income Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income (loss) before income taxes:
Income (loss) before income taxes	$ (1,504)	$ 61,093	$ 4,301	$ 57,460
Income tax provision (benefit)	(75)	14,173	2,205	12,694
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (1,429)	$ 46,920	$ 2,096	$ 44,766
Income tax provision as a percentage of income before income taxes	5.00%	23.20%	51.30%	22.10%
Other Effective Tax Rate Provision (Benefit)			$ 200

Stockholders' Equity (Share Buy

Stockholders' Equity (Share Buyback Program) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Aug. 04, 2020
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Value, Acquired, Cost Method	$ 5,756	$ 10,950	$ 1,073	$ 3,015
November 2014 Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Shares, Acquired (in Shares)	329,391		50,980		976,106	196,459
Treasury Stock, Value, Acquired, Cost Method	$ 5,800		$ 1,100		$ 16,700	$ 4,100
Subsequent Events | November 2014 Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Increase authorized for share buyback program							$ 20,000

Stockholders' Equity (The 2015

Stockholders' Equity (The 2015 Equity Incentive Plan) (Details) - The 2015 Equity Incentive Plan - shares	Jan. 01, 2020	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)		6,353,582
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,164,425

Stockholders' Equity (2014 Empl

Stockholders' Equity (2014 Employee Stock Purchase Plan) (Details) - USD ($) $ / shares in Units, $ in Thousands	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 [Line Items]
Allocated share based compensation	$ 6,513	$ 4,032	$ 11,795	$ 8,706
2014 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in Shares)	79,245		738,780
Weighted-Average Purchase Price (In Dollars per Share)	$ 15.84
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in Shares)	1,261,220		1,261,220
Allocated share based compensation	$ 300	$ 200	$ 400	$ 300

Stockholders' Equity (Key Assum

Stockholders' Equity (Key Assumptions Used in Determining Fair Value of Options Granted) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stockholders' Equity
Average volatility	44.00%	43.40%	43.10%	42.50%
Risk-free interest rate	0.50%	2.00%	0.80%	2.40%
Weighted-average expected life in years	4 years 10 months 24 days	5 years	5 years 8 months 12 days	5 years 8 months 12 days
Dividend yield rate	0.00%	0.00%	0.00%	0.00%

Stockholders' Equity (Summary o

Stockholders' Equity (Summary of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Options
Outstanding Options, Beginning of period				9,763,485
Options granted				1,789,254
Options exercised				(1,473,323)
Options cancelled				(84,203)
Options expired				(1,108,177)
Outstanding Options, End of period		8,887,036		8,887,036
Exercisable at the end of period		6,029,545		6,029,545
Weighted-Average Exercise Price
Outstanding Exercise Price (in dollars per share)				$ 15.26
Options granted (in dollars per share)				13.52
Options exercised (in dollars per share)				14.22
Options cancelled (in dollars per share)				16.53
Options expired (in dollars per share)				16.45
Outstanding Exercise Price (in dollars per share)		$ 14.92		14.92
Exercisable at the end of period (in dollars per share)		$ 14.31		$ 14.31
Additional Disclosures
Outstanding Contractual Term (in Years)				5 years 7 months 24 days
Outstanding Intrinsic Value		$ 66,980		$ 66,980
Exercisable remaining contractual term (in Years)				4 years 4 months 28 days
Exercisable aggregate intrinsic value		49,123		$ 49,123
Allocated share based compensation		6,513	$ 4,032	11,795	$ 8,706
Employee Stock Option
Additional Disclosures
Allocated share based compensation		2,600	$ 1,800	5,200	$ 4,200
Employee Stock Option | President, General Counsel and member of board of directors
Additional Disclosures
Allocated share based compensation		$ 700		$ 700
Vesting (percent)	80.00%

Stockholders' Equity (Informati

Stockholders' Equity (Information Relating to Option Grants and Exercises) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stockholders' Equity
Weighted-average grant date fair value (in Dollars per share)	$ 7.15	$ 8.17	$ 5.48	$ 8.46
Intrinsic value of options exercised	$ 6,486	$ 452	$ 6,974	$ 5,822
Cash received	19,088	1,108	20,339	5,047
Total fair value of the options vested during the year	$ 2,411	$ 388	$ 9,844	$ 7,502

Stockholders' Equity (Summary_2

Stockholders' Equity (Summary of Nonvested Options) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Options
Nonvested at beginning of period			2,747,133
Options granted			1,789,254
Options vested			(1,594,693)
Options forfeited			(84,203)
Nonvested at end of period	2,857,491		2,857,491
Weighted-Average Grant Date Fair Value
Nonvested at beginning of period (in dollars per share)			$ 6.99
Options granted (in dollars per share)	$ 7.15	$ 8.17	5.48	$ 8.46
Options vested (in dollars per share)			6.17
Options forfeited (in dollars per share)			7.13
Nonvested at end of period (in dollars per share)	$ 6.50		$ 6.50
Employee Consultant And Directors Stock Options
Weighted-Average Grant Date Fair Value
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 14.6		$ 14.6
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition			2 years 6 months

Stockholders' Equity (Restricte

Stockholders' Equity (Restricted Stock Units) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Contractual Term (in Years)				5 years 7 months 24 days
Allocated share based compensation		$ 6,513	$ 4,032	$ 11,795	$ 8,706
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				5 years
Allocated share based compensation		$ 3,600	$ 2,000	$ 6,000	$ 4,100
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition				2 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units, Number of Shares of Common Stock Per Award (in Shares)		1		1
Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options		$ 15,900		$ 15,900
President, General Counsel and member of board of directors | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation		$ 1,600		$ 1,600
Vesting (percent)	80.00%

Stockholders' Equity (Informa_2

Stockholders' Equity (Information Relating to RSU Grants and Deliveries) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)shares
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total RSUs outstanding at the beginning of the period	1,099,496
RSUs granted	727,746
RSUs forfeited	(35,792)
RSUs vested	(614,971)
Total RSUs outstanding at the end of the period	1,176,479
Stock surrendered to fulfill tax withholding obligations	235,053
Restricted Stock Units Issued as Compensation
Total Fair Market Value of RSUs Issued
RSUs granted (in Dollars) | $	$ 9,811

Stockholders' Equity (The 2018

Stockholders' Equity (The 2018 ANP Equity Incentive Plan) (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted					1,789,254
Outstanding Options, End of period	8,887,036		8,887,036		8,887,036
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term					5 years 7 months 24 days
Allocated share based compensation			$ 6,513	$ 4,032	$ 11,795	$ 8,706
The 2018 ANP Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term		10 years
Allocated share based compensation			$ 200		$ 300
The 2018 ANP Equity Incentive Plan | Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	2,433,445	3,648,932
Outstanding Options, End of period	5,918,777		5,918,777		5,918,777

Stockholders' Equity (Share-Bas

Stockholders' Equity (Share-Based Compensation Expense Included in the Statement of Operations) (Details) - USD ($) $ in Thousands	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 [Line Items]
Allocated share based compensation	$ 6,513	$ 4,032	$ 11,795	$ 8,706
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	970	959	2,329	2,238
Selling, distribution and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	123	95	230	189
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	5,052	2,648	8,271	5,439
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 368	$ 330	$ 965	$ 840

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Employee Benefits
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay			6.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.5	$ 0.4	$ 1	$ 0.7
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	0.90%		0.90%		0.90%
Defined Benefit Plan, Benefit Obligation	$ 2.5		$ 2.5		$ 2.4
Deferred compensation plan assets	0.5		0.5
Deferred compensation plan liabilities	$ 0.5		$ 0.5

Commitments and Contingencies (

Commitments and Contingencies (Purchase Commitments) (Details) - USD ($) $ in Thousands	1 Months Ended		6 Months Ended
	Nov. 30, 2012	Jan. 31, 2010	Jun. 30, 2020	Dec. 31, 2019
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Contractual Obligation			$ 46,697	$ 47,135
Commitments to Purchase Equipment and Raw Materials
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Long-term Purchase Commitment, Amount			50,000
Land-use rights | Commitment to invest
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Finite-lived Intangible Assets Acquired	$ 1,300	$ 1,200
Land-use rights | Commitment to develop land
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Contractual Obligation	$ 15,000
Payments for Construction in Process			$ 14,900

Litigation (Details)

Litigation (Details) $ in Millions	Jun. 27, 2019USD ($)	Sep. 30, 2011item
Pending Litigation [Member] | Enoxaparin Patent Litigation
Loss Contingencies [Line Items]
Number of Alleged Patent Infringements | item		2
Settled Litigation [Member]
Loss Contingencies [Line Items]
Litigation Settlement, amount paid to the Company | $	$ 59.9