Enanta Pharmaceuticals (ENTA) 10-Q 9 Feb 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2015	Jan. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Trading Symbol	ENTA
Entity Registrant Name	ENANTA PHARMACEUTICALS INC
Entity Central Index Key	1,177,648
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		18,925,311

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Current assets:
Cash and cash equivalents	$ 46,233	$ 21,726
Short-term marketable securities	133,786	123,479
Accounts receivable	17,869	15,289
Unbilled receivables	1,009	433
Deferred tax assets	1,581	1,447
Prepaid expenses and other current assets	8,543	8,267
Total current assets	209,021	170,641
Property and equipment, net	7,872	5,886
Long-term marketable securities	56,618	64,238
Deferred tax assets	4,260	4,640
Restricted cash	608	608
Total assets	278,379	246,013
Current liabilities:
Accounts payable	2,767	1,543
Accrued expenses and other current liabilities	3,165	3,962
Income taxes payable	4,940	1,199
Total current liabilities	10,872	6,704
Warrant liability	1,290	1,276
Other long-term liabilities	1,774	1,713
Total liabilities	$ 14,100	9,856
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock; $0.01 par value; 100,000,000 shares authorized; 18,795,114 and 18,716,834 shares issued and outstanding at December 31, 2015 and September 30, 2015, respectively	$ 188	187
Additional paid-in capital	232,111	229,957
Accumulated other comprehensive income (loss)	(189)	33
Retained earnings	32,169	5,980
Total stockholders' equity	264,279	236,157
Total liabilities and stockholders' equity	278,379	246,013
Series 1 Nonconvertible Preferred Stock [Member]
Current liabilities:
Series 1 nonconvertible preferred stock	$ 164	$ 163

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Sep. 30, 2015
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	18,795,114	18,716,834
Common stock, shares outstanding	18,795,114	18,716,834

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Milestone payments	$ 30,000	$ 75,000
Royalties	17,869	1,392
Other	576	1,106
Total revenue	48,445	77,498
Operating expenses:
Research and development	9,033	4,519
General and administrative	3,818	2,769
Total operating expenses	12,851	7,288
Income from operations	35,594	70,210
Other income:
Interest income	356	127
Interest expense	(12)	(2)
Change in fair value of warrant liability and Series 1 nonconvertible preferred stock, net	(15)	176
Total other income, net	329	301
Income before income taxes	35,923	70,511
Income tax expense	(9,734)	(28,502)
Net income	$ 26,189	$ 42,009
Net income per share:
Basic	$ 1.39	$ 2.26
Diluted	$ 1.36	$ 2.18
Weighted average common shares outstanding:
Basic	18,775,553	18,603,067
Diluted	19,269,357	19,283,223

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 26,189	$ 42,009
Other comprehensive income (loss):
Net unrealized gains (losses) on marketable securities, net of tax of $135 and $3	(222)	5
Total other comprehensive income (loss)	(222)	5
Comprehensive income	$ 25,967	$ 42,014

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net unrealized gains on marketable securities, tax	$ 135	$ 3

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income	$ 26,189	$ 42,009
Adjustments to reconcile net income to net cash used in operating activities:
Stock-based compensation expense	1,992	1,028
Amortization of premium on marketable securities	562	471
Deferred income taxes	382	11,487
Depreciation and amortization expense	339	129
Change in fair value of warrant liability and Series 1 nonconvertible preferred stock	15	(176)
Non-cash interest expense		2
Gain on sale of marketable securities		(1)
Income tax benefit from exercise of stock options		(1,919)
Premium on marketable securities	(171)	(169)
Changes in operating assets and liabilities:
Accounts receivable	(2,580)	(74,902)
Unbilled receivables	(576)	888
Prepaid expenses and other current assets	(276)	409
Accounts payable	149	(1,296)
Accrued expenses	150	(475)
Income taxes payable	3,741	16,896
Other long-term liabilities	77	9
Net cash provided by (used in) operating activities	29,993	(5,610)
Cash flows from investing activities
Purchases of property and equipment	(2,197)	(256)
Purchases of marketable securities	(34,622)	(8,153)
Sales of marketable securities		2,210
Maturities of marketable securities	31,187	13,226
Net cash provided by (used in) investing activities	(5,632)	7,027
Cash flows from financing activities
Proceeds from exercise of stock options	162	95
Payments of capital lease obligations	(16)
Income tax benefit from exercise of stock options		1,919
Net cash provided by financing activities	146	2,014
Net increase in cash and cash equivalents	24,507	3,431
Cash and cash equivalents at beginning of period	21,726	30,699
Cash and cash equivalents at end of period	46,233	34,130
Supplemental disclosure of cash flow information:
Cash paid for income taxes	5,707	66
Series 1 Nonconvertible Preferred Stock [Member]
Adjustments to reconcile net income to net cash used in operating activities:
Change in fair value of warrant liability and Series 1 nonconvertible preferred stock	$ 15	$ (176)

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Enanta Pharmaceuticals, Inc. (the “Company”), incorporated in Delaware in 1995, is a research and development-focused biotechnology company that uses its robust chemistry-driven approach and drug discovery capabilities to create small molecule drugs primarily for the treatment of viral infections and liver diseases. The Company has developed novel protease inhibitors for treatment of hepatitis C virus (“HCV”) infection. The Company also has clinical programs to develop cyclophilin and NS5A inhibitors targeted against HCV and a lead FXR agonist candidate for non-alcoholic steatohepatitis (“NASH”). Additionally, the Company has programs to discover new chemical entities, or compounds, for the treatment of hepatitis B virus (“HBV”) infection and respiratory syncytial virus (“RSV”) infection. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, the uncertainties of research and development, competition from technological innovations of others, dependence on collaborative arrangements, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance reporting capabilities. Unaudited Interim Financial Information The consolidated balance sheet at September 30, 2015 was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying unaudited consolidated financial statements as of December 31, 2015 and for the three months ended December 31, 2015 and 2014 have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended September 30, 2015. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of December 31, 2015 and results of operations for the three months ended December 31, 2015 and 2014 and cash flows for the three months ended December 31, 2015 and 2014 have been made. The results of operations for the three months ended December 31, 2015 are not necessarily indicative of the results of operations that may be expected for the year ending September 30, 2016. The accompanying consolidated financial statements have been prepared in conformity with GAAP. All dollar amounts in the consolidated financial statements and in the notes to the consolidated financial statements, except share and per share amounts, are in thousands unless otherwise indicated.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies For the Company’s Significant Accounting Policies refer to its Annual Report on Form 10-K for the fiscal year ended September 30, 2015. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, management’s judgments of separate units of accounting and best estimate of selling price of those units of accounting within its revenue arrangements; valuation of warrants, Series 1 nonconvertible preferred stock and stock-based awards; the useful lives of property and equipment; and the accounting for income taxes, including uncertain tax positions and the valuation of net deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates. Recently Issued Accounting Pronouncements In May, 2014, the Financial Accounting Standards Board (the “FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers In November 2015, the FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	3. Fair Value of Financial Assets and Liabilities The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of December 31, 2015 and September 30, 2015 and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value: Fair Value Measurements as of December 31, 2015 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 40,462 $ — $ — $ 40,462 U.S. Treasury notes 14,469 — — 14,469 Corporate bonds — 132,902 — 132,902 U.S. Agency bonds — 31,049 — 31,049 Commercial paper — 11,984 — 11,984 $ 54,931 $ 175,935 $ — $ 230,866 Liabilities: Warrant liability $ — $ — $ 1,290 $ 1,290 Series 1 nonconvertible preferred stock — — 164 164 $ — $ — $ 1,454 $ 1,454 Fair Value Measurements as of September 30, 2015 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 21,327 $ — $ — $ 21,327 Corporate bonds — 151,020 — 151,020 U.S. Agency bonds — 36,697 — 36,697 $ 21,327 $ 187,717 $ — $ 209,044 Liabilities: Warrant liability $ — $ — $ 1,276 $ 1,276 Series 1 nonconvertible preferred stock — — 163 163 $ — $ — $ 1,439 $ 1,439 During the three months ended December 31, 2015 and 2014, there were no transfers between Level 1, Level 2 and Level 3. As of December 31, 2015 and September 30, 2015, respectively, the warrant liability was comprised of the values of warrants for the purchase of Series 1 nonconvertible preferred stock measured at fair value. The outstanding Series 1 nonconvertible preferred stock was also measured at fair value. The fair value of both of these instruments was based on significant inputs not observable in the market, which represented a Level 3 measurement within the fair value hierarchy. The Company utilized a probability-weighted valuation model which takes into consideration various outcomes that may require the Company to transfer assets upon exercise. The fair value of outstanding warrants to purchase the Company’s Series 1 nonconvertible preferred stock was $1,290 and $1,276, at December 31, 2015 and September 30, 2015, respectively. The fair value of Series 1 nonconvertible preferred stock was $164 and $163 as of December 31, 2015 and September 30, 2015, respectively. Changes in the fair value of the warrant liability and Series 1 nonconvertible preferred stock are recognized in the consolidated statements of operations. As of December 31, 2015 and September 30, 2015, the recurring Level 3 fair value measurements of the Company’s warrant liability and Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs: December 31, 2015 Unobservable Input Range (Weighted Average) Warrant liability and Series 1 nonconvertible preferred stock Probabilities of payout 5% - 60% Periods in which payout is expected to occur 2016 – 2017 Discount rate 4.37% September 30, 2015 Unobservable Input Range (Weighted Average) Warrant liability and Series 1 nonconvertible preferred stock Probabilities of payout 5% - 60% Periods in which payout is expected to occur 2016 – 2017 Discount rate 4.25% The following table provides a rollforward of the aggregate fair values of the Company’s warrants for the purchase of Series 1 nonconvertible preferred stock and the outstanding Series 1 nonconvertible preferred stock for which fair value is determined by Level 3 inputs: Balance, September 30, 2015 $ 1,439 Increase in fair value 15 Balance, December 31, 2015 $ 1,454

Marketable Securities

Marketable Securities	3 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities As of December 31, 2015 and September 30, 2015, the fair value of available-for-sale marketable securities by type of security was as follows: December 31, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds $ 133,112 $ 8 $ (218 ) $ 132,902 U.S. Agency bonds 31,115 — (66 ) 31,049 U.S. Treasury notes 14,497 1 (29 ) 14,469 Commercial paper 11,984 — — 11,984 $ 190,708 $ 9 $ (313 ) $ 190,404 September 30, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds $ 151,012 $ 77 $ (69 ) $ 151,020 U.S. Agency bonds 36,652 45 — 36,697 $ 187,664 $ 122 $ (69 ) $ 187,717 As of December 31, 2015, marketable securities consisted of investments that mature within one year, with the exception of certain corporate bonds, which have maturities within three years and an aggregate fair value of $56,618.

Accrued Expenses and Other Long

Accrued Expenses and Other Long-Term Liabilities	3 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued Expenses and Other Long-Term Liabilities	5. Accrued Expenses and Other Long-Term Liabilities Accrued expenses (current) and other long-term liabilities consisted of the following as of December 31, 2015 and September 30, 2015: December 31, 2015 September 30, 2015 Accrued expenses: Accrued payroll and related expenses $ 789 $ 1,622 Accrued third-party license fee 500 — Accrued vendor manufacturing 433 18 Accrued fixed assets purchases 383 1,307 Accrued preclinical and clinical expenses 353 237 Accrued professional fees 304 338 Capital lease obligation 69 69 Accrued other 334 371 $ 3,165 $ 3,962 Other long-term liabilities: Accrued rent expense $ 646 $ 628 Capital lease obligation 513 529 Uncertain tax positions 498 448 Asset retirement obligation 117 108 $ 1,774 $ 1,713

Ongoing Collaboration Agreement

Ongoing Collaboration Agreements	3 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Ongoing Collaboration Agreements	6. Ongoing Collaboration Agreements AbbVie Collaboration The Company has a Collaborative Development and License Agreement (the “AbbVie Agreement”), as amended, with AbbVie Inc. to identify, develop and commercialize HCV NS3 and NS3/4A protease inhibitor compounds, including paritaprevir, under which it has received license payments, proceeds from a sale of preferred stock, research funding payments and milestone payments totaling $349,000 through December 31, 2015. As of December 31, 2015, the Company is eligible to receive additional milestone payments totaling up to $80,000 upon AbbVie’s achievement of commercialization regulatory approval milestones in the U.S. and other selected world markets for any additional protease inhibitor commercialized by AbbVie. Since the Company completed all its performance obligations under the AbbVie Agreement by the end of fiscal 2011, any milestone payments received since then have been and will be recognized as revenue when the milestones are achieved by AbbVie. The Company is also receiving annually tiered royalties per product ranging from the low double digits up to twenty percent, or on a blended basis from the low double digits up to the high teens, on calendar year net sales by AbbVie allocated to the collaboration’s protease inhibitors. Beginning with each January 1 the cumulative net sales of a given royalty-bearing product start at zero for purposes of calculating the tiered royalties. During the three months ended December 31, 2015, the Company earned and recognized as revenue a $30,000 milestone amount upon AbbVie’s achievement of commercialization regulatory approval of a paritaprevir-containing regimen in Japan. During the three months ended December 31, 2014, the Company earned and recognized as revenue a $75,000 milestone amount due from AbbVie as a result of U.S. FDA regulatory approval of AbbVie’s first HCV treatment regimen containing paritaprevir.

Warrants to Purchase Series 1 N

Warrants to Purchase Series 1 Nonconvertible Preferred Stock and Series 1 Nonconvertible Preferred Stock	3 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Warrants to Purchase Series 1 Nonconvertible Preferred Stock and Series 1 Nonconvertible Preferred Stock	7. Warrants to Purchase Series 1 Nonconvertible Preferred Stock and Series 1 Nonconvertible Preferred Stock In October and November 2010, the Company issued warrants to purchase up to a total of 1,999,989 shares of Series 1 nonconvertible preferred stock, which expire on October 4, 2017. As these warrants are free-standing financial instruments that may require the Company to transfer assets upon exercise, these warrants are classified as liabilities. The Company is required to remeasure the fair value of these preferred stock warrants at each reporting date, with any adjustments recorded within the change in fair value of warrant liability included in other income (expense) in the consolidated statement of operations. On February 5, 2014, 225,408 warrants were exercised resulting in the net issuance of 223,153 shares of Series 1 nonconvertible preferred stock.

Stock-Based Awards

Stock-Based Awards	3 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Awards	8. Stock-Based Awards The Company may grant stock-based awards under its existing 2012 Equity Incentive Plan (the “2012 Plan”) and its Employee Stock Purchase Plan (the “ESPP”). The Company also has outstanding stock-based awards under its 1995 Equity Incentive Plan (the “1995 Plan”), but is no longer granting awards under this plan. As of December 31, 2015, 554,679 shares of common stock are available for issuance under the 2012 Plan based on the target number of units awarded, none of which have yet vested. As of December 31, 2015, a total of 185,614 shares of common stock are available for issuance under the ESPP. As of December 31, 2015, the Company had not commenced any offering under the ESPP and no shares have been issued. The Company applies the fair value recognition provisions for all stock-based awards granted or modified in accordance with authoritative guidance. Under this guidance the Company records compensation costs over the requisite service period of the award based on the grant-date fair value. The straight-line method is applied to all grants with service conditions, while the graded vesting method is applied to all grants with both service and performance conditions. Shares Issuable Under Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding as of September 30, 2015 1,752,010 $ 23.76 7.2 $ 25,093 Granted 401,280 31.42 Exercised (78,280 ) 2.07 Forfeited (5,531 ) 36.01 Outstanding as of December 31, 2015 2,069,479 $ 26.03 7.7 $ 19,496 Options vested and expected to vest as of December 31, 2015 1,887,232 $ 27.03 7.7 $ 16,293 Options exercisable as of December 31, 2015 843,731 $ 17.13 5.9 $ 14,359 In December 2015, the Company awarded certain executive officers a total of 50,000 share units consisting of 25,000 performance share units, or PSUs, and 25,000 relative total shareholder return units, or rTSRUs. The number of units represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number. The PSUs will vest and result in issuance, or settlement, of common shares, based upon continued employment and achievement of specified research and development milestones on or before December 31, 2017. The aggregate grant date fair value of the 25,000 PSUs ranges between $0 and $1,602. During the three months ended December 31, 2015, the Company recorded no compensation expense related to the PSU awards as none of the performance-based targets was probable of being achieved during this period. The rTSRUs will vest and result in the issuance of common stock based on continuing employment and the relative ranking of the total shareholder return, or TSR, of the Company’s common stock in relation to the TSR of the component companies in the NASDAQ Biotech Index over a two-year period based on a comparison of average closing stock prices in November 2015 and December 2017. The number of market-based rTSRUs awarded represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number. The Company used a Monte Carlo simulation model to estimate that the grant-date fair value of the rTSRUs was $942. The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value: Risk-free interest rate 0.97% Dividend yield 0% Expected volatility 63.95% Remaining performance period (years) 2.03 Estimated fair value per share of rTSRUs granted $37.67 The fair value related to the rTSRUs will be recorded as compensation expense over the period from date of grant to December 2017 regardless of whether the target relative total shareholder returns are reached. In addition, in December 2015, the Company awarded an executive officer 5,250 share units consisting of 2,625 PSUs and 2,625 rTSRUs. The number of units represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number. The PSUs will vest and result in issuance, or settlement, of common shares, based upon continued employment and achievement of specified research and development milestones on or before December 31, 2016. The aggregate grant date fair value of the 2,625 PSUs ranges between $0 and $168. During the three months ended December 31, 2015, the Company recorded no compensation expense related to the PSU awards as none of the performance-based targets was probable of being achieved during this period. The rTSRUs will vest and result in the issuance of common stock based on continuing employment and the relative ranking of the total shareholder return, or TSR, of the Company’s common stock in relation to the TSR of the component companies in the NASDAQ Biotech Index over a two-year period based on a comparison of average closing stock prices in December 2014 and December 2016. The number of market-based rTSRUs awarded represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0% to 200% of the target number. The Company used a Monte Carlo simulation model to estimate that the grant-date fair value of the rTSRUs was $44. The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value: Risk-free interest rate 0.65% Dividend yield 0% Expected volatility 72.30% Remaining performance period (years) 1.03 Estimated fair value per share of rTSRUs granted $16.90 The fair value related to the rTSRUs will be recorded as compensation expense over the period from date of grant to December 2016 regardless of whether the target relative total shareholder returns are reached. The Company recognized stock-based compensation expense on all awards in the following expense categories: Three Months Ended December 31, 2015 2014 Research and development $ 714 $ 242 General and administrative 1,278 786 $ 1,992 $ 1,028 As of December 31, 2015, the Company had an aggregate of $24,166 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 3.1 years.

Net Income Per Share

Net Income Per Share	3 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income Per Share	9. Net Income Per Share Basic and diluted net income per share attributable to common stockholders was calculated as follows for the three months ended December 31, 2015 and 2014: Three Months Ended December 31, 2015 2014 Basic net income per share: Numerator: Net income $ 26,189 $ 42,009 Denominator: Weighted average common shares outstanding—basic 18,775,553 18,603,067 Net income per share—basic $ 1.39 $ 2.26 Diluted net income per share: Numerator: Net income $ 26,189 $ 42,009 Denominator: Weighted average common shares outstanding—basic 18,775,553 18,603,067 Dilutive effect of common stock equivalents 493,804 680,156 Weighted average common shares outstanding—diluted 19,269,357 19,283,223 Net income per share—diluted $ 1.36 $ 2.18 Stock options and awards for the purchase of 1,119,345 and 288,490 weighted average shares were excluded from the computation of diluted net income per share attributable to common stockholders for the three months ended December 31, 2015 and 2014, respectively, because those options had an anti-dilutive impact due to the assumed proceeds per share using the treasury stock method being greater than the average fair value of the Company’s common shares for those periods.

Income Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes For the three months ended December 31, 2015 and December 31, 2014, the Company recorded an income tax provision of $9,734 and $28,502, respectively, representing an effective tax rate of 27.1% and 40.4%, respectively. The income tax provision for the three months ended December 31, 2015 and 2014 was primarily attributable to the tax provision on the earnings of the Company’s domestic operations. For the three months ended December 31, 2015 the Company’s effective tax rate differs from the statutory rate of 35% primarily due to reinstatement of the federal research and development tax credits. For the three months ended December 31, 2014 the Company’s effective tax rate differs from the statutory rate of 35% primarily due to state income taxes and certain expenditures which are permanently not deductible for tax purposes. The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are still open under statute from 2008 to the present. Earlier years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods. The Company had an unrecognized tax benefit of $498 and $448 as of December 31, 2015 and September 30, 2015, respectively. Unrecognized tax benefits represent tax positions for which reserves have been established. The Company’s policy is to record interest and penalties related to uncertain tax positions as part of its income tax provision.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Leases The Company has an office and laboratory lease that expires in September 2022. Payment escalation as specified in the lease agreement is accrued such that rent expense is recognized on a straight-line basis over the term of occupancy. The Company recorded rent expense of $506 and $237 for the three months ended December 31, 2015 and 2014, respectively. In connection with the lease, the Company has outstanding a $608 letter of credit, collateralized by a money market account. As of December 31, 2015 and September 30, 2015, the Company classified $608 related to the letter of credit as restricted cash. Additionally, the lease, as amended, included a $598 tenant improvement allowance from the landlord, which allowance is accounted for as a capital lease obligation. Intellectual Property Licenses The Company has a non-exclusive intellectual property license agreement with a third party, under which the Company is required to pay (1) annual maintenance fees of $105 for each year that the agreement remains in effect, commencing on the first anniversary of the agreement, in order to maintain the right to use the license, and (2) a one-time fee of $50 in each circumstance in which the Company provides the licensed intellectual property to one of its collaborators with the prior consent of the licensor. The Company also has a non-exclusive license with respect to patents it uses in its HCV research. Under the license, the Company is obligated to pay milestones totaling up to $5,000, plus low single digit royalties, for the development and regulatory approval of each HCV product outside of the Company’s collaboration with AbbVie and any other collaboration it may enter into in the future with a partner that has already licensed these patents. During the three months ended December 31, 2015 the Company became obligated for a $500 milestone payment under this license agreement upon its filing to commence clinical development of its cyclophilin inhibitor candidate. During the three months ended December 31, 2014, no events triggering such payment occurred. Litigation and Contingencies Related to Use of Intellectual Property From time to time, the Company may become subject to legal proceedings, claims and litigation arising in the ordinary course of business. The Company currently is not a party to any threatened or pending litigation. However, third parties might allege that the Company or its collaborators are infringing their patent rights or that the Company is otherwise violating their intellectual property rights. Such third parties may resort to litigation against the Company or its collaborators, which the Company has agreed to indemnify. With respect to some of these patents, the Company expects that it will be required to obtain licenses and could be required to pay license fees or royalties, or both. These licenses may not be available on acceptable terms, or at all. A costly license, or inability to obtain a necessary license, would have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company accrues contingent liabilities when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. Indemnification Agreements In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to customers, vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements, from services to be provided by the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. In addition, the Company maintains officers and directors insurance coverage. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its financial statements as of December 31, 2015.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, management’s judgments of separate units of accounting and best estimate of selling price of those units of accounting within its revenue arrangements; valuation of warrants, Series 1 nonconvertible preferred stock and stock-based awards; the useful lives of property and equipment; and the accounting for income taxes, including uncertain tax positions and the valuation of net deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In May, 2014, the Financial Accounting Standards Board (the “FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers In November 2015, the FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

Fair Value of Financial Asset20

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities that were Subject to Fair Value Measurement on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of December 31, 2015 and September 30, 2015 and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value: Fair Value Measurements as of December 31, 2015 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 40,462 $ — $ — $ 40,462 U.S. Treasury notes 14,469 — — 14,469 Corporate bonds — 132,902 — 132,902 U.S. Agency bonds — 31,049 — 31,049 Commercial paper — 11,984 — 11,984 $ 54,931 $ 175,935 $ — $ 230,866 Liabilities: Warrant liability $ — $ — $ 1,290 $ 1,290 Series 1 nonconvertible preferred stock — — 164 164 $ — $ — $ 1,454 $ 1,454 Fair Value Measurements as of September 30, 2015 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 21,327 $ — $ — $ 21,327 Corporate bonds — 151,020 — 151,020 U.S. Agency bonds — 36,697 — 36,697 $ 21,327 $ 187,717 $ — $ 209,044 Liabilities: Warrant liability $ — $ — $ 1,276 $ 1,276 Series 1 nonconvertible preferred stock — — 163 163 $ — $ — $ 1,439 $ 1,439
Fair Value Measurements of the Company's Warrant Liability and Series 1 Nonconvertible Preferred Stock	As of December 31, 2015 and September 30, 2015, the recurring Level 3 fair value measurements of the Company’s warrant liability and Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs: December 31, 2015 Unobservable Input Range (Weighted Average) Warrant liability and Series 1 nonconvertible preferred stock Probabilities of payout 5% - 60% Periods in which payout is expected to occur 2016 – 2017 Discount rate 4.37% September 30, 2015 Unobservable Input Range (Weighted Average) Warrant liability and Series 1 nonconvertible preferred stock Probabilities of payout 5% - 60% Periods in which payout is expected to occur 2016 – 2017 Discount rate 4.25%
Rollforward of Aggregate Fair Values of Warrants	The following table provides a rollforward of the aggregate fair values of the Company’s warrants for the purchase of Series 1 nonconvertible preferred stock and the outstanding Series 1 nonconvertible preferred stock for which fair value is determined by Level 3 inputs: Balance, September 30, 2015 $ 1,439 Increase in fair value 15 Balance, December 31, 2015 $ 1,454

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Fair Value of Available-for-Sale Marketable Securities by Type of Security	As of December 31, 2015 and September 30, 2015, the fair value of available-for-sale marketable securities by type of security was as follows: December 31, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds $ 133,112 $ 8 $ (218 ) $ 132,902 U.S. Agency bonds 31,115 — (66 ) 31,049 U.S. Treasury notes 14,497 1 (29 ) 14,469 Commercial paper 11,984 — — 11,984 $ 190,708 $ 9 $ (313 ) $ 190,404 September 30, 2015 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds $ 151,012 $ 77 $ (69 ) $ 151,020 U.S. Agency bonds 36,652 45 — 36,697 $ 187,664 $ 122 $ (69 ) $ 187,717

Accrued Expenses and Other Lo22

Accrued Expenses and Other Long-Term Liabilities (Tables)	3 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued Expenses (Current) and Other Long-Term Liabilities	Accrued expenses (current) and other long-term liabilities consisted of the following as of December 31, 2015 and September 30, 2015: December 31, 2015 September 30, 2015 Accrued expenses: Accrued payroll and related expenses $ 789 $ 1,622 Accrued third-party license fee 500 — Accrued vendor manufacturing 433 18 Accrued fixed assets purchases 383 1,307 Accrued preclinical and clinical expenses 353 237 Accrued professional fees 304 338 Capital lease obligation 69 69 Accrued other 334 371 $ 3,165 $ 3,962 Other long-term liabilities: Accrued rent expense $ 646 $ 628 Capital lease obligation 513 529 Uncertain tax positions 498 448 Asset retirement obligation 117 108 $ 1,774 $ 1,713

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	3 Months Ended
	Dec. 31, 2015
Stock Option Activity	The straight-line method is applied to all grants with service conditions, while the graded vesting method is applied to all grants with both service and performance conditions. Shares Issuable Under Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding as of September 30, 2015 1,752,010 $ 23.76 7.2 $ 25,093 Granted 401,280 31.42 Exercised (78,280 ) 2.07 Forfeited (5,531 ) 36.01 Outstanding as of December 31, 2015 2,069,479 $ 26.03 7.7 $ 19,496 Options vested and expected to vest as of December 31, 2015 1,887,232 $ 27.03 7.7 $ 16,293 Options exercisable as of December 31, 2015 843,731 $ 17.13 5.9 $ 14,359
Stock-Based Compensation Expense	The Company recognized stock-based compensation expense on all awards in the following expense categories: Three Months Ended December 31, 2015 2014 Research and development $ 714 $ 242 General and administrative 1,278 786 $ 1,992 $ 1,028
Certain Executives [Member] | RTSRUs [Member]
Weighted Average Assumptions Used To Value Awards and Estimated Grant Date Fair Value	The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value: Risk-free interest rate 0.97% Dividend yield 0% Expected volatility 63.95% Remaining performance period (years) 2.03 Estimated fair value per share of rTSRUs granted $37.67
Executive Officer [Member] | RTSRUs [Member]
Weighted Average Assumptions Used To Value Awards and Estimated Grant Date Fair Value	The table below sets forth the assumptions used to value the awards and the estimated grant-date fair value: Risk-free interest rate 0.65% Dividend yield 0% Expected volatility 72.30% Remaining performance period (years) 1.03 Estimated fair value per share of rTSRUs granted $16.90

Net Income Per Share (Tables)

Net Income Per Share (Tables)	3 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Basic and Diluted Net Income Per Share Attributable to Common Stockholders	Basic and diluted net income per share attributable to common stockholders was calculated as follows for the three months ended December 31, 2015 and 2014: Three Months Ended December 31, 2015 2014 Basic net income per share: Numerator: Net income $ 26,189 $ 42,009 Denominator: Weighted average common shares outstanding—basic 18,775,553 18,603,067 Net income per share—basic $ 1.39 $ 2.26 Diluted net income per share: Numerator: Net income $ 26,189 $ 42,009 Denominator: Weighted average common shares outstanding—basic 18,775,553 18,603,067 Dilutive effect of common stock equivalents 493,804 680,156 Weighted average common shares outstanding—diluted 19,269,357 19,283,223 Net income per share—diluted $ 1.36 $ 2.18

Fair Value of Financial Asset25

Fair Value of Financial Assets and Liabilities - Financial Assets and Liabilities that were Subject to Fair Value Measurement on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Assets:
Cash equivalents	$ 40,462	$ 21,327
Available for sale securities, fair value	190,404	187,717
Assets, Fair Value Disclosure, Total	230,866	209,044
Liabilities:
Liabilities	1,454	1,439
Liabilities, Fair Value Disclosure, Total	1,454	1,439
U.S. Treasury Notes [Member]
Assets:
Available for sale securities, fair value	14,469
Corporate Bonds [Member]
Assets:
Available for sale securities, fair value	132,902	151,020
U.S. Agency Bonds [Member]
Assets:
Available for sale securities, fair value	31,049	36,697
Commercial Paper [Member]
Assets:
Available for sale securities, fair value	11,984
Warrant Liability [Member]
Liabilities:
Liabilities	1,290	1,276
Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	164	163
Level 1 [Member]
Assets:
Cash equivalents	40,462	21,327
Assets, Fair Value Disclosure, Total	54,931	21,327
Level 1 [Member] | U.S. Treasury Notes [Member]
Assets:
Available for sale securities, fair value	14,469
Level 2 [Member]
Assets:
Assets, Fair Value Disclosure, Total	175,935	187,717
Level 2 [Member] | Corporate Bonds [Member]
Assets:
Available for sale securities, fair value	132,902	151,020
Level 2 [Member] | U.S. Agency Bonds [Member]
Assets:
Available for sale securities, fair value	31,049	36,697
Level 2 [Member] | Commercial Paper [Member]
Assets:
Available for sale securities, fair value	11,984
Level 3 [Member]
Liabilities:
Liabilities, Fair Value Disclosure, Total	1,454	1,439
Level 3 [Member] | Warrant Liability [Member]
Liabilities:
Liabilities	1,290	1,276
Level 3 [Member] | Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	$ 164	$ 163

Fair Value of Financial Asset26

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1, Level 2 and Level 3	$ 0	$ 0
Fair value of Series 1 nonconvertible preferred stock	1,454,000		$ 1,439,000
Series 1 Nonconvertible Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Series 1 nonconvertible preferred stock	164,000		163,000
Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of Series 1 nonconvertible preferred stock	$ 1,290,000		$ 1,276,000

Fair Value of Financial Asset27

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of the Company's Warrant Liability and Series 1 Nonconvertible Preferred Stock (Detail) - Warrant Liability [Member] - Series 1 Nonconvertible Preferred Stock [Member]	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Periods in which payout is expected to occur, beginning	2,016	2,016
Periods in which payout is expected to occur, ending	2,017	2,017
Discount rate	4.37%	4.25%
Minimum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Probabilities of payout	5.00%	5.00%
Maximum [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Probabilities of payout	60.00%	60.00%

Fair Value of Financial Asset28

Fair Value of Financial Assets and Liabilities - Rollforward of Aggregate Fair Values of Warrants (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2015USD ($)
Fair Value Disclosures [Abstract]
Beginning Balance	$ 1,439
Increase in fair value	15
Ending Balance	$ 1,454

Marketable Securities - Fair Va

Marketable Securities - Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 190,708	$ 187,664
Gross Unrealized Gains	9	122
Gross Unrealized Losses	(313)	(69)
Fair Value	190,404	187,717
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	133,112	151,012
Gross Unrealized Gains	8	77
Gross Unrealized Losses	(218)	(69)
Fair Value	132,902	151,020
U.S. Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	31,115	36,652
Gross Unrealized Gains		45
Gross Unrealized Losses	(66)
Fair Value	31,049	$ 36,697
U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,497
Gross Unrealized Gains	1
Gross Unrealized Losses	(29)
Fair Value	14,469
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,984
Fair Value	$ 11,984

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable securities maturing in greater than one year, aggregate fair value	$ 56,618	$ 64,238

Accrued Expenses and Other Lo31

Accrued Expenses and Other Long-Term Liabilities - Accrued Expenses (Current) and Other Long-Term Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Accrued expenses:
Accrued payroll and related expenses	$ 789	$ 1,622
Accrued third-party license fee	500
Accrued vendor manufacturing	433	18
Accrued fixed assets purchases	383	1,307
Accrued preclinical and clinical expenses	353	237
Accrued professional fees	304	338
Capital lease obligation	69	69
Accrued other	334	371
Accrued expenses	3,165	3,962
Other long-term liabilities:
Accrued rent expense	646	628
Capital lease obligation	513	529
Uncertain tax positions	498	448
Asset retirement obligation	117	108
Other long-term liabilities	$ 1,774	$ 1,713

Ongoing Collaboration Agreeme32

Ongoing Collaboration Agreements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized	$ 30,000	$ 75,000
AbbVie [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement tiered royalty description	From the low double digits up to twenty percent, or on a blended basis from the low double digits up to the high teens, on calendar year net sales
Additional Funding Agreement Terms [Member] | AbbVie [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue payment received	$ 80,000
Milestone Payments [Member] | AbbVie [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceed received to fund research activities and preferred stock financing	349,000
Milestone revenue recognized		$ 75,000
Milestone Payments [Member] | Paritaprevir 3-DAA Regimen [Member] | AbbVie [Member] | JAPAN
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized	$ 30,000

Warrants to Purchase Series 133

Warrants to Purchase Series 1 Nonconvertible Preferred Stock and Series 1 Nonconvertible Preferred Stock - Additional Information (Detail) - Series 1 Nonconvertible Preferred Stock [Member] - shares	Feb. 05, 2014	Dec. 31, 2015	Nov. 30, 2010
Class of Warrant or Right [Line Items]
Number of shares issuable upon exercise of the warrants			1,999,989
Warrant expiration date		Oct. 4, 2017
Warrant exercised	225,408
Warrants issuance	223,153

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2015USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate of unrecognized stock-based compensation cost | $	$ 24,166,000
Weighted average recognition period	3 years 1 month 6 days
Certain Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	50,000
Certain Executives [Member] | PSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	25,000
Compensation expenses | $	$ 0
Certain Executives [Member] | PSU [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value of award | $	0
Certain Executives [Member] | PSU [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value of award | $	$ 1,602,000
Certain Executives [Member] | RTSRUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	25,000
Aggregate grant date fair value of award | $	$ 942,000
Certain Executives [Member] | RTSRUs [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares range percentage	0.00%
Certain Executives [Member] | RTSRUs [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares range percentage	200.00%
Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	5,250
Executive Officer [Member] | PSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	2,625
Compensation expenses | $	$ 0
Executive Officer [Member] | PSU [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value of award | $	0
Executive Officer [Member] | PSU [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value of award | $	$ 168,000
Executive Officer [Member] | RTSRUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares awarded | shares	2,625
Aggregate grant date fair value of award | $	$ 44,000
Executive Officer [Member] | RTSRUs [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares range percentage	0.00%
Executive Officer [Member] | RTSRUs [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares range percentage	200.00%
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant | shares	185,614
Shares issued | shares	0
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant | shares	554,679

Stock-Based Awards - Stock Opti

Stock-Based Awards - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2015	Dec. 31, 2015
Shares Issuable Under Options
Outstanding as of beginning of period		1,752,010
Granted		401,280
Exercised		(78,280)
Forfeited		(5,531)
Outstanding as of end of period	1,752,010	2,069,479
Options vested and expected to vest as of end of period		1,887,232
Options exercisable as of end of period		843,731
Weighted Average Exercise Price
Outstanding as of beginning of period		$ 23.76
Granted		31.42
Exercised		2.07
Forfeited		36.01
Outstanding as of ending balance	$ 23.76	26.03
Options vested and expected to vest as of end of period		27.03
Options exercisable as of end of period		$ 17.13
Weighted Average Remaining Contractual Term (In years)
Outstanding as of end of period	7 years 2 months 12 days	7 years 8 months 12 days
Options vested and expected to vest as of end period		7 years 8 months 12 days
Options exercisable as of end of period		5 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding as of beginning of period		$ 25,093
Outstanding as of end of period	$ 25,093	19,496
Options vested and expected to vest as of end of period		16,293
Options exercisable as of end of period		$ 14,359

Stock-Based Awards - Weighted A

Stock-Based Awards - Weighted Average Assumptions Used To Value Awards and Estimated Grant Date Fair Value (Detail) - RTSRUs [Member]	3 Months Ended
	Dec. 31, 2015$ / shares
Certain Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.97%
Dividend yield	0.00%
Expected volatility	63.95%
Remaining performance period (years)	2 years 11 days
Estimated fair value per share of rTSRUs granted	$ 37.67
Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.65%
Dividend yield	0.00%
Expected volatility	72.30%
Remaining performance period (years)	1 year 11 days
Estimated fair value per share of rTSRUs granted	$ 16.90

Stock-Based Awards - Stock-Base

Stock-Based Awards - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,992	$ 1,028
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	714	242
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,278	$ 786

Net Income Per Share - Basic an

Net Income Per Share - Basic and Diluted Net Income Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Basic net income per share:
Net income	$ 26,189	$ 42,009
Weighted average common shares outstanding-basic	18,775,553	18,603,067
Net income per share-basic	$ 1.39	$ 2.26
Diluted net income per share:
Net income	$ 26,189	$ 42,009
Weighted average common shares outstanding-basic	18,775,553	18,603,067
Dilutive effect of common stock equivalents	493,804	680,156
Weighted average common shares outstanding-diluted	19,269,357	19,283,223
Net income per share-diluted	$ 1.36	$ 2.18

Net Income Per Share - Addition

Net Income Per Share - Additional Information (Detail) - shares	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Stock Options and Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the computation of diluted net income per share	1,119,345	288,490

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 9,734	$ 28,502
Effective income tax rate	27.10%	40.40%
Federal statutory income tax rate	35.00%	35.00%
Unrecognized tax benefits	$ 498		$ 448

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense		$ 237,000
Office lease expiration period	Sep. 30, 2022
Outstanding letter of credit	$ 608,000		$ 608,000
Restricted cash	608,000		$ 608,000
Tenant improvement allowance	598,000
Maintenance fees	105,000
One-time fee	50,000
Company's obligation to pay	5,000,000
Milestone payment liability incurred	$ 500,000	$ 0