Relypsa (RLYP) 10-Q 7 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	1-May-14
Document And Entity Information [Line Items]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Trading Symbol	'RLYP	'
Entity Registrant Name	'Relypsa Inc	'
Entity Central Index Key	'0001416792	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	33,845,329

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$26,098	$94,759
Short-term investments	52,819	'
Other receivables	861	241
Prepaid expenses and other current assets	1,316	1,657
Total current assets	81,094	96,657
Property and equipment, net	6,182	5,624
Intangible assets	10	14
Other assets	3,970	3,736
Total assets	91,256	106,031
Current liabilities:	'	'
Accounts payable	4,513	4,736
Accrued payroll and related expenses	1,470	1,794
Accrued liabilities	6,062	5,947
Deferred rent, current portion	746	640
Line of credit, current portion	414	408
Capital loan, current portion	4,772	4,304
Total current liabilities	17,977	17,829
Long-term liabilities:	'	'
Deferred rent, long-term	4,734	4,394
Line of credit	545	630
Capital loan	7,211	8,328
Total liabilities	30,467	31,181
Commitments and contingencies	'	'
Stockholders’ equity:	'	'
Preferred stock: $0.001 par value; 5,000 shares authorized at March 31, 2014 and December 2013; no shares issued and outstanding at March 31, 2014 and December 31, 2013	'	'
Common stock: $0.001 par value; 300,000 shares authorized at March 31, 2014 and December 31, 2013; 29,711 and 29,710 shares issued and outstanding at March 31, 2014 and December 31, 2013, respectively	30	30
Additional paid-in capital	302,663	300,660
Accumulated other comprehensive income	4	'
Deficit accumulated during the development stage	-241,908	-225,840
Total stockholders’ equity	60,789	74,850
Total liabilities and stockholders’ equity	$91,256	$106,031

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Per Share data, unless otherwise specified
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	300,000	300,000
Common stock, shares issued	29,711	29,710
Common stock, shares outstanding	29,711	29,710

Condensed_Statements_of_Operat

Condensed Statements of Operations (USD $)	3 Months Ended		77 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating expenses:	'	'	'
Research and development	$10,909	$22,604	$179,033
General and administrative	4,795	2,535	40,608
Acquired in-process research and development	0	'	6,823
Total operating expenses	15,704	25,139	226,464
Loss from operations	-15,704	-25,139	-226,464
Interest and other income (expense), net	27	-864	-436
Interest expense	-391	-248	-5,324
Net loss	-16,068	-26,251	-232,224
Preferred stock extinguishment	0	'	9,711
Deemed dividend to preferred stockholders	0	'	-26,052
Net loss attributable to common stockholders	($16,068)	($26,251)	($248,565)
Net loss per share attributable to common stockholders, basic and diluted	($0.54)	($84.61)	'
Weighted average common shares used to compute net loss per share attributable to common stockholders, basic and diluted	29,710,415	310,275	'

Condensed_Statements_of_Compre

Condensed Statements of Comprehensive Loss (USD $)	3 Months Ended		77 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Net loss	($16,068)	($26,251)	($232,224)
Other comprehensive income (loss):	'	'	'
Unrealized gain (loss) on available-for-sale securities, net of tax	4	-11	4
Total comprehensive loss	($16,064)	($26,262)	($232,220)

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	3 Months Ended		77 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating activities	'	'	'
Net loss	($16,068)	($26,251)	($232,224)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation and amortization	263	327	5,760
Loss on disposal of property and equipment	'	'	103
Acquired in-process research and development	0	'	6,823
Stock-based compensation	1,998	394	9,280
Amortization of debt issuance costs	9	5	212
Amortization of debt discount	37	21	173
Accretion of final debt payment	95	'	445
Investment premium amortization	148	'	148
Conversion of bridge financing interest into Series B preferred stock	'	'	130
Revaluation of convertible preferred stock warrant liability	'	900	1,861
Changes in assets and liabilities:	'	'	'
Other receivables	-620	2,534	-861
Prepaid expenses and other current assets	332	-291	-1,458
Other assets	-234	-69	-4,041
Accounts payable	-690	713	4,045
Accrued and other liabilities	-209	938	8,290
Deferred rent	446	676	5,480
Net cash used in operating activities	-14,493	-20,103	-195,834
Investing activities	'	'	'
Purchase of short-term investments	-52,963	-10,215	-179,102
Proceeds from maturities of short-term investments	'	15,182	126,139
Purchase of property and equipment	-350	-2,904	-8,181
Net cash (used in) provided by investing activities	-53,313	2,063	-61,144
Financing activities	'	'	'
Net proceeds from issuance of convertible preferred stock	'	'	185,653
Net proceeds from initial public offering	'	'	77,964
Proceeds from bridge debt financing	'	'	6,100
Proceeds from common stock option exercise	5	1	689
Proceeds from warrant exercise	'	'	397
Net proceeds from capital loan	'	12,219	21,404
Repayment of capital loan	-760	'	-10,029
Net proceeds from equipment line of credit	'	'	2,700
Repayment of equipment line of credit	-100	'	-1,802
Net cash (used in) provided by financing activities	-855	12,220	283,076
Net increase (decrease) in cash and cash equivalents	-68,661	-5,820	26,098
Cash and cash equivalents at beginning of period	94,759	15,221	'
Cash and cash equivalents at end of period	26,098	9,401	26,098
Noncash investing and financing activities	'	'	'
Change in unrealized (loss) gain on short-term investments	4	-11	4
Reclassification of convertible preferred stock warrant liability due to the exercise of the warrants	'	'	28,072
Reclassification of convertible preferred stock warrant liability due to the conversion to warrants to purchase common stock	'	'	575
Conversion of bridge financing into preferred stock	'	'	6,100
Tangible and intangible assets acquired with preferred stock	'	'	10,229
Property and equipment purchased under capital lease	'	'	875
Accounts payable related to purchase of property and equipment	467	'	467
Line of Credit	'	'	'
Noncash investing and financing activities	'	'	'
Issuance of warrants in connection	'	'	42
Capital Loan	'	'	'
Noncash investing and financing activities	'	'	'
Issuance of warrants in connection	'	193	347
Series B Bridge Financing	'	'	'
Noncash investing and financing activities	'	'	'
Issuance of warrants in connection	'	'	345
Series C Financing	'	'	'
Noncash investing and financing activities	'	'	'
Issuance of warrants in connection	'	'	$26,052

Description_of_Business_and_Si

Description of Business and Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Description of Business and Significant Accounting Policies	'
	1.  Description of Business and Significant Accounting Policies
	Organization
	Relypsa, Inc. (Relypsa or the Company) is a biopharmaceutical company dedicated to the development and commercialization of new non-absorbed polymeric drugs for important applications in renal, cardiovascular and metabolic disease. The Company commenced operations on October 29, 2007 and is considered a development stage company. The Company’s principal operations are based in Redwood City, California and it operates in one segment.
	The information included in this quarterly report on Form 10-Q should be read in conjunction with the financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 filed with the U.S. Securities Exchange Commission (SEC).
	On April 16, 2014, the Company completed its underwritten public offering of 4,130,611 shares of common stock at an offering price of $24.50 per share. The Company received aggregate net proceeds of approximately $94.4 million, after deducting the underwriting discounts and estimated offering related transaction costs. The financial statements as of March 31, 2014, including share and per share amounts, do not include the effects of the offering.
	Basis of Presentation
	There have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2014 as compared to the significant accounting policies described in the Company’s audited financial statements included in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2013.
	The accompanying financial information for the three months ended March 31, 2014 is unaudited. These unaudited interim condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In management’s opinion, the unaudited interim condensed financial statements have been prepared on the same basis as the audited financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013, and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our statement of financial position as of March 31, 2014, our statements of operations and comprehensive loss for the three months ended March 31, 2014 and our statements of cash flows for the three months ended March 31, 2014. The results for the three months ended March 31, 2014 are not necessarily indicative of the results expected for the full fiscal year or any other period(s).
	Use of Estimates
	The preparation of these unaudited interim condensed financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
	Liquidity
	In the course of its development activities, the Company has sustained significant operating losses and expects such losses to continue over the next few years. The Company’s success depends on the outcome of its research and development activities. From October 29, 2007 (inception) through March 31, 2014, the Company has incurred cumulative net losses of $232.2 million. Management expects to incur additional losses in the future to conduct product research and development and to conduct commercialization activities. Additional funding will be needed to support the planned commercial launch in the United States and as the Company builds out its sales capabilities. The Company intends to raise such funding through the issuance of additional equity, debt financings or other sources, such as strategic collaborations. However, if such financing is not available at adequate levels or on acceptable terms, the Company could be required to significantly reduce operating expenses and delay, reduce the scope of or eliminate some of its development programs or its commercialization efforts, enter into a collaboration or other similar arrangement with respect to commercialization rights to patiromer or any of its other product candidates, out-license intellectual property rights to patiromer or its other product candidates and sell unsecured assets, or a combination of the above, which may have a material adverse effect on the Company’s business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all.
	Cash Equivalents
	The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of purchase to be cash equivalents.
	Short-Term Investments
	Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than 365 days from the date of acquisition. Short-term investments are carried at fair value based upon quoted market prices or pricing models for similar securities. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated comprehensive income (loss). Realized gains or losses on the sale of all such securities are reported in interest and other income (expense), net and computed using the specific identification method.
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities including salaries and related employee benefits, costs associated with clinical trials, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on behalf of the Company.
	Clinical Trial Accruals
	Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.
	Contract Manufacturing Accruals
	Contract Manufacturing costs are a component of research and development expenses. The Company accrues and expenses contract manufacturing activities performed by third parties based upon actual or the estimated amount of work completed in accordance with agreements established with contract manufacturing organizations. The Company determines the actual costs or it estimates the costs through discussions with internal personnel and external service providers as to the manufacturing activities that were performed or completed and the agreed-upon fee to be paid for such services.
	Stock-Based Compensation
	The Company accounts for stock-based compensation based on the fair value of the share-based awards that are ultimately expected to vest. The fair value of employee stock options granted is estimated on the date of grant using the Black-Scholes option pricing model, and is recognized in expense over the service period using the straight-line method, net of estimated forfeitures. Forfeiture estimates are adjusted to the extent that actual forfeitures differ from the prior estimates.
	The fair value of restricted stock unit awards used in our expense recognition method is based on the number of shares granted and the closing price of our common stock on the date of the grant. Such value is recognized as an expense over the service period using the straight-line method, net of estimated forfeitures.
	The Company records the expense attributed to nonemployee services paid with share-based awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees is subject to periodic adjustments as the options vest, and the expense is recognized over the period during which services are received.
	Net Loss per Common Share Attributable to Common Stockholders
	Basic and diluted net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive.
	The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands):
		March 31,		March 31,
		2014		2013
	Convertible preferred stock — as converted to common stock		—		17,281
	Warrants to purchase convertible preferred stock — as converted to common stock		—		2,291
	Warrants to purchase common stock		64		—
	Options to purchase common stock		3,610		2,188
	Restricted stock units		5		—
	Common stock subject to repurchase		4		6
			3,683		21,766

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
Fair Value Measurements	'
	2.  Fair Value Measurements
	Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. There is a three-level valuation hierarchy for disclosure of fair value measurements, as follows:
	Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.
	Level 2 – Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life.
	Level 3 – Unobservable inputs that are supported by little or no market activity and reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.
	A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
	The following tables set forth the fair value of the Company’s financial instruments that were measured at fair value on a recurring basis as of March 31, 2014 and December 31, 2013 (in thousands):
		Level 1		Level 2		Level 3		Total
	31-Mar-14
	Financial assets:
	Money market funds	$	19,466	$	—	$	—	$	19,466
	Corporate bonds		—		34,737		—		34,737
	Commercial paper		—		23,896		—		23,896
	Total financial assets	$	19,466	$	58,633	$	—	$	78,099
		Level 1		Level 2		Level 3		Total
	31-Dec-13
	Financial assets:
	Money market funds	$	93,523	$	—	$	—	$	93,523
	Total financial assets	$	93,523	$	—	$	—	$	93,523
	Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds as Level 1. When quoted market prices are not available for the specific security, then the Company estimates fair value by using benchmark yields, reported trades, broker/dealer quotes, and issuer spreads; these securities are classified as Level 2. The Company classifies corporate bonds, commercial paper and certificates of deposit as Level 2. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3.
	The carrying values of the Company’s financial instruments, such as cash equivalents, other receivables, accounts payable, accrued liabilities and debt approximate fair value due to the short-term nature of these items. The fair value of the debt was determined by discounting the contractual cash flows at the current rates charged for similar debt instruments (Level 3).
	There were no transfers between Level 1 and Level 2 during the periods presented.

Cash_Cash_Equivalents_and_Shor

Cash, Cash Equivalents, and Short-Term Investments	3 Months Ended
	Mar. 31, 2014
Cash, Cash Equivalents, and Short-Term Investments	'
	3.  Cash, Cash Equivalents, and Short-Term Investments
	The following is a summary of cash, cash equivalents, and short-term investments (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	31-Mar-14
	Cash and money market funds	$	20,284	$	—	$	—		$	20,284
	Corporate bonds		34,749		—		(12	)		34,737
	Commercial paper		23,880		16		—			23,896
	Total financial assets	$	78,913	$	16	$	(12	)	$	78,917
	Reported as:
	Cash and cash equivalents								$	26,098
	Short-term investments									52,819
									$	78,917
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	31-Dec-13
	Cash and money market funds	$	94,759	$	—	$	—		$	94,759
	Total financial assets	$	94,759	$	—	$	—		$	94,759
	Reported as:
	Cash and cash equivalents								$	94,759
									$	94,759
	For the three months ended March 31, 2014 and the year ended December 31, 2013, there were no realized gains or losses on the available-for-sale securities. All available-for-sale marketable securities held at March 31, 2014 have maturity dates less than one year. There were no available-for-sale marketable securities held by the Company at December 31, 2013.
	All of the Company’s available-for-sale marketable securities are subject to a periodic impairment review. The Company considers a marketable debt security to be impaired when its fair value is less than its carrying cost, in which case the Company would further review the investment to determine whether it is other-than-temporarily impaired. When the Company evaluates an investment for other-than-temporary impairment, the Company reviews factors such as the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer and any changes thereto, intent to sell, and whether it is more likely than not the Company will be required to sell the investment before the recovery of its cost basis. If an investment is other-than-temporarily impaired, the Company writes it down through earnings to its impaired value and establishes that as a new cost basis for the investment. The Company did not identify any of its available-for-sale marketable securities as other-than-temporarily impaired in any of the periods presented. As of March 31, 2014, no investment was in a continuous unrealized loss position for more than one year, the unrealized losses were not due to change in credit risk and the Company believes that is more likely than not the investments will be held until maturity or a forecasted recovery of fair value.

Borrowings

Borrowings	3 Months Ended
	Mar. 31, 2014
Borrowings	'
	4.  Borrowings
	Capital Loan
	On January 31, 2013, the Company entered into a Loan and Security Agreement that provides the Company with a loan of up to $20.0 million. Per the terms of the Loan and Security Agreement there are two advances available, an initial advance of $12.5 million that was received in January 2013 and a second advance of $7.5 million. The Company received the initial advance and, on December 19, 2013, the Company entered into an amendment to the loan and security agreement to extend the draw period of the second advance to June 30, 2014. The second advance became available upon achievement of the primary endpoints of pivotal Phase 3 trial for patiromer, but has not been drawn down as of March 31, 2014. The terms of the loan require interest only payments through December 31, 2013, followed by 30 equal monthly payments of interest and principal. The Company will be required to make a final payment upon loan maturity of 6% of the amounts advanced. The interest rate for the first advance is 7.80% and the interest rate on the second advance will be the three month LIBOR rate plus 7.44%. In addition, the Company issued a warrant to purchase 54,437 shares of Series C-1 convertible preferred stock upon the receipt of the initial advance. Upon the Company’s IPO in November 2013, the warrants to purchase convertible preferred stock were converted to warrants to purchase common stock. As of March 31, 2014, these warrants were still outstanding.
	The fair value of the warrants issued in connection with the initial advance of $0.2 million at the issuance date was estimated using the Black-Scholes model with the following assumptions: a risk-free interest rate of 1.38%, a life of 7 years, a volatility factor of 91.4%, and no dividend yield. This amount is recorded as a debt discount, which will be amortized into interest expense over the repayment period. Interest expense was $0.4 million for the three months ended March 31, 2014.
	The loan and security agreement includes customary operating but non-financial covenants, including limitations on the Company’s ability to incur additional indebtedness, issue dividends and transfer or encumber any collateral securing the debt, as well as a cross-default provision with regard to the Company’s equipment line of credit. As of March 31, 2014, principal of $11.7 million was outstanding under the loan and security agreement, and the Company was in compliance with all required covenants.
	Line of Credit
	In May 2013, the Company entered into a $1.6 million equipment line of credit with a bank. The terms of repayment are 36 monthly payments, and the interest rate is fixed at 5.75%. The Company will be required to make a final payment of 9.25% of the amounts advanced. The outstanding balance on the credit line is secured by a first priority lien over all equipment purchased using the line of credit. In connection with the Company’s equipment line of credit, the Company issued a warrant to purchase 6,968 shares of Series C-1 convertible preferred stock. Upon the Company’s IPO in November 2013, the warrants to purchase convertible preferred stock were converted to warrants to purchase common stock. As of March 31, 2014, these warrants were still outstanding.
	The fair value of the warrants of $25,000 at the issuance date was estimated using the Black-Scholes model with the following assumptions: a risk-free interest rate of 1.07%, a life of 7 years, a volatility factor of 91.6%, and no dividend yield. This amount is recorded as a debt discount, which will be amortized into interest expense over the repayment period. Interest expense was approximately $40,000  for the three months ended March 31, 2014.
	The equipment line of credit includes customary operating but non-financial covenants, including limitations on the Company’s ability to incur additional indebtedness, issue dividends and transfer or encumber any collateral securing the debt, as well as a cross-default provision with regard to the Company’s term loan. The Company utilized $1.3 million of the line of credit in the second quarter of 2013, and the remaining $0.3 million balance available under the line of credit expired unused on June 30, 2013. As of March 31, 2014, principal of $0.9 million was outstanding under the line of credit, and the Company was in compliance with all required covenants.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies	'
	5.  Commitments and Contingencies
	Contract Manufacturing and Supply Agreement
	On November 27, 2012, Relypsa entered into a Memorandum of Understanding (MOU) with Lanxess Corporation (Lanxess), pursuant to which Lanxess serves as a commercial manufacturer and commercial supplier of the active ingredient of patiromer. The MOU was amended on June 27, 2013 and September 30, 2013 (the Amended MOU) to include updated estimates of costs and timing of activities being conducted by the Company and Lanxess.
	On January 9, 2014, the Company entered into a Manufacturing and Supply Agreement (the Supply Agreement) with Lanxess that supersedes the Amended MOU. Under the Supply Agreement, Lanxess has agreed to manufacture and supply for commercial sale the drug substance for patiromer. The Supply Agreement terminates on December 31, 2020 unless terminated earlier. The Company may extend the Supply Agreement for an additional five years with notice. The Supply Agreement may be terminated (i) by the Company with notice if it abandons development or manufacturing of patiromer or fails to obtain FDA approval or the parties disagree regarding the feasibility or price of certain specification changes, or with notice at least 24 months in advance, which may be given after October 1, 2015, (ii) by Lanxess with notice if the Company fails to issue certain purchase orders, or with notice at least 24 months in advance, which may be given after October 1, 2015 and (iii) by either party with notice in the event of certain delays by the other party in performing its material obligations, or with notice if the parties fail to timely agree on certain price terms beginning in September 2015.
	During 2013, the Company paid Lanxess for plant modifications that are required to support the manufacturing scale up of patiromer in anticipation of commercial launch. These payments are recorded in other assets and prior to the commercialization of patiromer, these payments will be amortized to research and development expenses in accordance with the period over which the Company expects to derive future economic value. Lanxess will have full ownership of the purchased equipment and may manufacture other products with the modified plant when not occupied by patiromer.
	Under the Supply Agreement, Lanxess is obligated to manufacture the Company’s commercial supply of patiromer, and the Company is obligated to purchase from Lanxess such products manufactured, pursuant to the terms and conditions of the Supply Agreement. Relypsa is obligated to make certain minimum purchases of drug substance and raw materials over the two years totaling $24.0 million. The forecasted payments on an annual basis are expected to be $12.2 million and $11.8 million during 2014 and 2015, respectively. In addition, the Company will be required to purchase an additional $12.3 million of drug substance from Lanxess if Lanxess meets certain requirements as defined by the Supply Agreement.

Technology_Agreement

Technology Agreement	3 Months Ended
	Mar. 31, 2014
Technology Agreement	'
	6.  Technology Agreement
	During 2007, the Company acquired certain assets from Ilypsa, Inc. (Ilypsa), a wholly owned subsidiary of Amgen, Inc. (Amgen), consisting of certain property and equipment and intangible assets primarily relating to Ilypsa’s non-absorbed polymer therapeutics clinical development programs. In consideration for such transfer the Company issued 476,686 shares of Series A convertible preferred stock to Amgen valued at $8.2 million. Contingent consideration included an obligation to pay royalties on sales of products resulting from the clinical development programs. This transaction was accounted for as an asset acquisition with the cost of the acquisition allocated to the individual assets acquired on a relative fair value basis.
	During November 2009, the Company purchased from Ilypsa certain rights Ilypsa had retained in one of the clinical development programs that the Company had acquired in 2007 under an amended intellectual property agreement. In consideration, the Company issued to Ilypsa 214,186 shares of Series A convertible preferred stock with a fair value of $2.0 million. This amount was recorded as in-process research and development and was recognized in expense, as the related clinical program is still in development and has no alternative future use.
	During February 2013, the Company dosed its first patient in a pivotal clinical trial that is evaluating patiromer for the treatment of hyperkalemia. Upon achieving this milestone the Company was required to make a one-time milestone payment of $12.5 million to Ilypsa (Amgen). The Company recognized a one-time charge to research and development expense of $12.5 million related to the required milestone payment. Upon a change in control transaction, an additional payment could be owed to Ilypsa (Amgen) ranging from 6.7% to 10% of the purchase price, less certain expenses, up to a total of $30.0 million. The Company has no obligation to make any further milestone payments or to pay royalties on future sales of patiromer to Ilypsa (Amgen).

Equity_Compensation_Plans_and_

Equity Compensation Plans and Stock Based Compensation	3 Months Ended
	Mar. 31, 2014
Equity Compensation Plans and Stock Based Compensation	'
	7.  Equity Compensation Plans and Stock Based Compensation
	The Company adopted the 2007 Equity Incentive Plan (the 2007 Plan) which provides for the granting of stock options to employees, directors and consultants of the Company. Options granted under the 2007 Plan may be either incentive stock options or nonqualified stock options. Incentive stock options may be granted only to Company employees. Nonqualified stock options may be granted to Company employees, outside directors and consultants. Options under the 2007 Plan may be granted for periods of up to ten years and are exercisable immediately, subject to rights of repurchase by the Company, which lapse over the period the applicable shares vest. Employee options granted by the Company generally vest over four years.
	As of November 2013, the Company’s stockholders approved the 2013 Equity Incentive Plan (the 2013 Plan). The number of shares which may be issued or transferred under the Plan shall be equal to the sum of 1,276,587 shares and any of the shares available for issuance under the 2007 Plan. Options granted under the 2013 Plan may be granted for periods of up to ten years to become exercisable when vested. As of March 31, 2014, the Company has reserved 1,162,902 shares of common stock for issuance under the 2013 Plan.
	The following table summarizes option activity under the 2013 Plan and related information (in thousands, except per share and contractual term amounts):
		Shares			Shares Subject			Weighted-		Weighted-		Aggregate
		Available			to Outstanding			Average		Average		Intrinsic
		for			Options			Exercise Price		Remaining		Value
		Grant								Contractual
										Term
										(in years)
	Options Outstanding at December 31, 2013		1,233			3,545		$	5.63
	Options granted		(77	)		77			36.4
	Restricted stock units granted		(5	)		—			—
	Options exercised		—			—			—
	Options forfeited		12			(12	)		21.46
	Balances at March 31, 2014		1,163			3,610		$	6.24		8.4	$	85,600
	Vested and expected to vest at March 31, 2014					3,472		$	6.15		8.3	$	82,621
	Vested at March 31, 2014					1,301		$	4.13		7.3	$	33,400
	The weighted-average grant-date estimated fair value of options granted during the three months ended March 31, 2014 and 2013 was $30.44 and $3.78 per share, respectively. At March 31, 2014 and December 31, 2013, there were 3,904 and 5,125 shares of common stock outstanding, respectively, subject to the Company’s right of repurchase at prices ranging from $3.96 to $7.40 per share. At March 31, 2014 and December 31, 2013, the Company recorded $18,000 and $23,000, respectively, as liabilities associated with shares issued with repurchase rights. The aggregate intrinsic value of options outstanding and exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of Relypsa’s common stock of $29.81 per share as of March 31, 2014.
	Stock-Based Compensation
	Stock-based compensation expense included in the Company’s statements of operations is as follows (in thousands):
		Three Months Ended March 31,
		2014			2013
	Research and development:
	Employees	$	225		$	144
	Nonemployee consultants		1,209			28
	General and administrative:
	Employees		564			222
	Total stock-based compensation expense	$	1,998		$	394
	As of March 31, 2014, the Company had $20.0 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over an estimated weighted-average period of 2.8 years.
	The estimated grant date fair value of employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions:
		Three Months Ended March 31,
		2014			2013
	Expected volatility		109%			94.70%
	Expected dividends		0%			0%
	Expected term (in years)		6.25			6.25
	Risk-free rate		1.84% –1.91 %			1.14%
	The fair value of nonemployee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions:
		Three Months Ended March 31,
		2014			2013
	Expected volatility		106.96%-122.32%			81.90%
	Expected dividends		0%			0%
	Expected term (in years)		6.1 – 9.3			8.2 – 9.5
	Risk-free rate		1.96% – 2.59%			1.47 – 1.76%
	Restricted Stock Units
	The Company began granting restricted stock unit awards subject to performance vesting criteria to employees starting in 2014. Restricted stock unit awards consist of the right to receive shares of common stock, subject to achievement of time-based criteria and certain corporate performance-related goals over a specified period. The fair value of restricted stock unit awards is measured based on the number of shares granted and the closing market price of our common stock on the date of grant.
	The following table summarizes restricted stock unit activity for the three months ended March 31, 2014 (in thousands, except per share amounts):
		Restricted Stock Units
		Number of Shares			Weighted Average
					Grant Date Fair
					Value Per Share
	Nonvested at December 31, 2013		—		$	—
	Granted		5			32.37
	Vested		—			—
	Canceled		—			—
	Nonvested at March 31, 2014		5		$	32.37
	As of March 31, 2014, none of the restricted stock units granted by the Company have vested.

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2014
Subsequent Events	'
	8.  Subsequent Events
	Public Offering
	On April 16, 2014, the Company completed its underwritten public offering of 4,130,611 shares of common stock at an offering price of $24.50 per share.The Company received aggregate net proceeds of approximately $94.4 million, after deducting the underwriting discounts and estimated offering related transaction costs. The financial statements as of March 31, 2014, including share and per share amounts, do not include the effects of the offering.
	The table below shows, on a pro forma basis, the impact of the Company’s offering on certain condensed balance sheet items. The as adjusted condensed balance sheet data below gives effect to the sale of 4,130,611 shares of common stock from the offering at the offering price of $24.50 per share, after deducting the underwriting discounts and commissions and estimated offering related transaction expenses.
		As of March 31, 2014
		Actual			As Adjusted
			(unaudited)
			(in thousands)
	Balance Sheet Data:
	Cash, cash equivalents and short-term investments	$	78,917		$	173,345
	Working capital		63,117			157,545
	Total assets		91,256			185,684
	Accumulated deficit		(241,908	)		(241,908	)
	Total stockholders’ equity		60,789			155,217
	Lease amendment
	On April 24, 2014, the Company amended its operating lease agreement due to the Company electing to draw down an additional $0.8 million in landlord funded lease-hold improvements. Pursuant to the lease amendment, the base rent shall be increased to include the amortized additional landlord funded lease-hold improvements of $0.2 million per year until the expiration of the lease on December 31, 2019.

Description_of_Business_and_Si1

Description of Business and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Organization	'
	Organization
	Relypsa, Inc. (Relypsa or the Company) is a biopharmaceutical company dedicated to the development and commercialization of new non-absorbed polymeric drugs for important applications in renal, cardiovascular and metabolic disease. The Company commenced operations on October 29, 2007 and is considered a development stage company. The Company’s principal operations are based in Redwood City, California and it operates in one segment.
	The information included in this quarterly report on Form 10-Q should be read in conjunction with the financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 filed with the U.S. Securities Exchange Commission (SEC).
	On April 16, 2014, the Company completed its underwritten public offering of 4,130,611 shares of common stock at an offering price of $24.50 per share. The Company received aggregate net proceeds of approximately $94.4 million, after deducting the underwriting discounts and estimated offering related transaction costs. The financial statements as of March 31, 2014, including share and per share amounts, do not include the effects of the offering.
Basis of Presentation	'
	Basis of Presentation
	There have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2014 as compared to the significant accounting policies described in the Company’s audited financial statements included in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2013.
	The accompanying financial information for the three months ended March 31, 2014 is unaudited. These unaudited interim condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP and applicable rules and regulations of the SEC regarding interim financial reporting. Certain information and note disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In management’s opinion, the unaudited interim condensed financial statements have been prepared on the same basis as the audited financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013, and include all adjustments, which include only normal recurring adjustments necessary for the fair presentation of our statement of financial position as of March 31, 2014, our statements of operations and comprehensive loss for the three months ended March 31, 2014 and our statements of cash flows for the three months ended March 31, 2014. The results for the three months ended March 31, 2014 are not necessarily indicative of the results expected for the full fiscal year or any other period(s).
Use of Estimates	'
	Use of Estimates
	The preparation of these unaudited interim condensed financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Liquidity	'
	Liquidity
	In the course of its development activities, the Company has sustained significant operating losses and expects such losses to continue over the next few years. The Company’s success depends on the outcome of its research and development activities. From October 29, 2007 (inception) through March 31, 2014, the Company has incurred cumulative net losses of $232.2 million. Management expects to incur additional losses in the future to conduct product research and development and to conduct commercialization activities. Additional funding will be needed to support the planned commercial launch in the United States and as the Company builds out its sales capabilities. The Company intends to raise such funding through the issuance of additional equity, debt financings or other sources, such as strategic collaborations. However, if such financing is not available at adequate levels or on acceptable terms, the Company could be required to significantly reduce operating expenses and delay, reduce the scope of or eliminate some of its development programs or its commercialization efforts, enter into a collaboration or other similar arrangement with respect to commercialization rights to patiromer or any of its other product candidates, out-license intellectual property rights to patiromer or its other product candidates and sell unsecured assets, or a combination of the above, which may have a material adverse effect on the Company’s business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all.
Cash Equivalents	'
	Cash Equivalents
	The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of purchase to be cash equivalents.
Short-Term Investments	'
	Short-Term Investments
	Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than 365 days from the date of acquisition. Short-term investments are carried at fair value based upon quoted market prices or pricing models for similar securities. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated comprehensive income (loss). Realized gains or losses on the sale of all such securities are reported in interest and other income (expense), net and computed using the specific identification method.
Research and Development Expenses	'
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities including salaries and related employee benefits, costs associated with clinical trials, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on behalf of the Company.
Clinical Trial Accruals	'
	Clinical Trial Accruals
	Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.
Contract Manufacturing Accruals	'
	Contract Manufacturing Accruals
	Contract Manufacturing costs are a component of research and development expenses. The Company accrues and expenses contract manufacturing activities performed by third parties based upon actual or the estimated amount of work completed in accordance with agreements established with contract manufacturing organizations. The Company determines the actual costs or it estimates the costs through discussions with internal personnel and external service providers as to the manufacturing activities that were performed or completed and the agreed-upon fee to be paid for such services.
Stock-Based Compensation	'
	Stock-Based Compensation
	The Company accounts for stock-based compensation based on the fair value of the share-based awards that are ultimately expected to vest. The fair value of employee stock options granted is estimated on the date of grant using the Black-Scholes option pricing model, and is recognized in expense over the service period using the straight-line method, net of estimated forfeitures. Forfeiture estimates are adjusted to the extent that actual forfeitures differ from the prior estimates.
	The fair value of restricted stock unit awards used in our expense recognition method is based on the number of shares granted and the closing price of our common stock on the date of the grant. Such value is recognized as an expense over the service period using the straight-line method, net of estimated forfeitures.
	The Company records the expense attributed to nonemployee services paid with share-based awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees is subject to periodic adjustments as the options vest, and the expense is recognized over the period during which services are received.
Net Loss per Common Share Attributable to Common Stockholders	'
	Net Loss per Common Share Attributable to Common Stockholders
	Basic and diluted net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive.
	The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands):
		March 31,		March 31,
		2014		2013
	Convertible preferred stock — as converted to common stock		—		17,281
	Warrants to purchase convertible preferred stock — as converted to common stock		—		2,291
	Warrants to purchase common stock		64		—
	Options to purchase common stock		3,610		2,188
	Restricted stock units		5		—
	Common stock subject to repurchase		4		6
			3,683		21,766

Description_of_Business_and_Si2

Description of Business and Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2014
Schedule of Shares Excluded from Computations of Diluted Net Loss per Common Share	'
	The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands):
		March 31,		March 31,
		2014		2013
	Convertible preferred stock — as converted to common stock		—		17,281
	Warrants to purchase convertible preferred stock — as converted to common stock		—		2,291
	Warrants to purchase common stock		64		—
	Options to purchase common stock		3,610		2,188
	Restricted stock units		5		—
	Common stock subject to repurchase		4		6
			3,683		21,766

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis	'
	The following tables set forth the fair value of the Company’s financial instruments that were measured at fair value on a recurring basis as of March 31, 2014 and December 31, 2013 (in thousands):
		Level 1		Level 2		Level 3		Total
	31-Mar-14
	Financial assets:
	Money market funds	$	19,466	$	—	$	—	$	19,466
	Corporate bonds		—		34,737		—		34,737
	Commercial paper		—		23,896		—		23,896
	Total financial assets	$	19,466	$	58,633	$	—	$	78,099
		Level 1		Level 2		Level 3		Total
	31-Dec-13
	Financial assets:
	Money market funds	$	93,523	$	—	$	—	$	93,523
	Total financial assets	$	93,523	$	—	$	—	$	93,523

Cash_Cash_Equivalents_and_Shor1

Cash, Cash Equivalents, and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2014
Summary of Cash, Cash Equivalents, and Short-Term Investments	'
	The following is a summary of cash, cash equivalents, and short-term investments (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	31-Mar-14
	Cash and money market funds	$	20,284	$	—	$	—		$	20,284
	Corporate bonds		34,749		—		(12	)		34,737
	Commercial paper		23,880		16		—			23,896
	Total financial assets	$	78,913	$	16	$	(12	)	$	78,917
	Reported as:
	Cash and cash equivalents								$	26,098
	Short-term investments									52,819
									$	78,917
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	31-Dec-13
	Cash and money market funds	$	94,759	$	—	$	—		$	94,759
	Total financial assets	$	94,759	$	—	$	—		$	94,759
	Reported as:
	Cash and cash equivalents								$	94,759
									$	94,759

Equity_Compensation_Plans_and_1

Equity Compensation Plans and Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Summary of Option Activity	'
	The following table summarizes option activity under the 2013 Plan and related information (in thousands, except per share and contractual term amounts):
		Shares			Shares Subject			Weighted-		Weighted-		Aggregate
		Available			to Outstanding			Average		Average		Intrinsic
		for			Options			Exercise Price		Remaining		Value
		Grant								Contractual
										Term
										(in years)
	Options Outstanding at December 31, 2013		1,233			3,545		$	5.63
	Options granted		(77	)		77			36.4
	Restricted stock units granted		(5	)		—			—
	Options exercised		—			—			—
	Options forfeited		12			(12	)		21.46
	Balances at March 31, 2014		1,163			3,610		$	6.24		8.4	$	85,600
	Vested and expected to vest at March 31, 2014					3,472		$	6.15		8.3	$	82,621
	Vested at March 31, 2014					1,301		$	4.13		7.3	$	33,400
Schedule of Stock-Based Compensation Expense	'
	Stock-based compensation expense included in the Company’s statements of operations is as follows (in thousands):
		Three Months Ended March 31,
		2014			2013
	Research and development:
	Employees	$	225		$	144
	Nonemployee consultants		1,209			28
	General and administrative:
	Employees		564			222
	Total stock-based compensation expense	$	1,998		$	394
Summary of Restricted Stock Unit Activity	'
	The following table summarizes restricted stock unit activity for the three months ended March 31, 2014 (in thousands, except per share amounts):
		Restricted Stock Units
		Number of Shares			Weighted Average
					Grant Date Fair
					Value Per Share
	Nonvested at December 31, 2013		—		$	—
	Granted		5			32.37
	Vested		—			—
	Canceled		—			—
	Nonvested at March 31, 2014		5		$	32.37
Employee Stock Option	'
Schedule of Valuation Assumptions Used to Calculate Fair Value of Stock Options	'
	The estimated grant date fair value of employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions:
		Three Months Ended March 31,
		2014			2013
	Expected volatility		109%			94.70%
	Expected dividends		0%			0%
	Expected term (in years)		6.25			6.25
	Risk-free rate		1.84% –1.91 %			1.14%
Non Employee Stock Option	'
Schedule of Valuation Assumptions Used to Calculate Fair Value of Stock Options	'
	The fair value of nonemployee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions:
		Three Months Ended March 31,
		2014			2013
	Expected volatility		106.96%-122.32%			81.90%
	Expected dividends		0%			0%
	Expected term (in years)		6.1 – 9.3			8.2 – 9.5
	Risk-free rate		1.96% – 2.59%			1.47 – 1.76%

Subsequent_Events_Tables

Subsequent Events (Tables)	3 Months Ended
	Mar. 31, 2014
Schedule of Adjusted Condensed Balance Sheet Data	'
	The table below shows, on a pro forma basis, the impact of the Company’s offering on certain condensed balance sheet items. The as adjusted condensed balance sheet data below gives effect to the sale of 4,130,611 shares of common stock from the offering at the offering price of $24.50 per share, after deducting the underwriting discounts and commissions and estimated offering related transaction expenses.
		As of March 31, 2014
		Actual			As Adjusted
			(unaudited)
			(in thousands)
	Balance Sheet Data:
	Cash, cash equivalents and short-term investments	$	78,917		$	173,345
	Working capital		63,117			157,545
	Total assets		91,256			185,684
	Accumulated deficit		(241,908	)		(241,908	)
	Total stockholders’ equity		60,789			155,217

Description_of_Business_and_Si3

Description of Business and Significant Accounting Policies - Additional Information (Details) (USD $)	3 Months Ended		77 Months Ended	0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Apr. 16, 2014
	Segment			Subsequent Event
Description Of Business And Significant Accounting Policies [Line Items]	'	'	'	'
Number of business segments	1	'	'	'
Issuance of common stock, shares	'	'	'	4,130,611
Shares issued, price per share	'	'	'	$24.50
Aggregate net proceeds from issuance of common stock	'	'	'	$94,400,000
Cumulative net losses	$16,068,000	$26,251,000	$232,224,000	'

Description_of_Business_and_Si4

Description of Business and Significant Accounting Policies - Schedule of Shares Excluded from Computations of Diluted Net Loss per Common Share (Details)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	3,683	21,766
Convertible Preferred Stock - As Converted to Common Stock	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	'	17,281
Warrants to Purchase Convertible Preferred Stock - As Converted to Common Stock	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	'	2,291
Warrants To Purchase Common Stock	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	64	'
Options to Purchase Common Stock	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	3,610	2,188
Restricted Stock Units	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	5	'
Common Stock Subject to Repurchase	'	'
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]	'	'
Common stock equivalents excluded from computations of diluted net loss per common share	4	6

Fair_Value_Measurements_Fair_V

Fair Value Measurements - Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial assets:	'	'
Total financial assets	$78,099	$93,523
Level 1	'	'
Financial assets:	'	'
Total financial assets	19,466	93,523
Level 2	'	'
Financial assets:	'	'
Total financial assets	58,633	'
Corporate Bonds	'	'
Financial assets:	'	'
Total financial assets	34,737	'
Corporate Bonds | Level 2	'	'
Financial assets:	'	'
Total financial assets	34,737	'
Money Market Funds	'	'
Financial assets:	'	'
Total financial assets	19,466	93,523
Money Market Funds | Level 1	'	'
Financial assets:	'	'
Total financial assets	19,466	93,523
Commercial Paper	'	'
Financial assets:	'	'
Total financial assets	23,896	'
Commercial Paper | Level 2	'	'
Financial assets:	'	'
Total financial assets	$23,896	'

Cash_Cash_Equivalents_and_Shor2

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents, and Short-Term Investments (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Cash And Cash Equivalents [Line Items]	'	'	'	'
Amortized Cost	$78,913	$94,759	'	'
Gross Unrealized Gains	16	'	'	'
Gross Unrealized Losses	-12	'	'	'
Estimated Fair Value	78,917	94,759	'	'
Cash and cash equivalents	26,098	94,759	9,401	15,221
Short-term investments	52,819	'	'	'
Total financial assets	78,917	94,759	'	'
Cash and Money Market Funds	'	'	'	'
Cash And Cash Equivalents [Line Items]	'	'	'	'
Amortized Cost	20,284	94,759	'	'
Gross Unrealized Gains	'	'	'	'
Gross Unrealized Losses	'	'	'	'
Estimated Fair Value	20,284	94,759	'	'
Commercial Paper	'	'	'	'
Cash And Cash Equivalents [Line Items]	'	'	'	'
Amortized Cost	23,880	'	'	'
Gross Unrealized Gains	16	'	'	'
Estimated Fair Value	23,896	'	'	'
Corporate Bonds	'	'	'	'
Cash And Cash Equivalents [Line Items]	'	'	'	'
Amortized Cost	34,749	'	'	'
Gross Unrealized Losses	-12	'	'	'
Estimated Fair Value	$34,737	'	'	'

Cash_Cash_Equivalents_and_Shor3

Cash, Cash Equivalents, and Short-Term Investments - Additional Information (Details) (Maximum)	3 Months Ended
	Mar. 31, 2014
Maximum	'
Cash And Cash Equivalents [Line Items]	'
Available-for-sale marketable securities maturity dates	'1 year

Borrowings_Additional_Informat

Borrowings - Additional Information (Details) (USD $)

3 Months Ended

77 Months Ended

3 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

Mar. 31, 2013

Mar. 31, 2014

31-May-13

Mar. 31, 2014

Jun. 30, 2013

31-May-13

Mar. 31, 2014

Jan. 31, 2013

Jan. 31, 2013

Mar. 31, 2014

Jan. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Line of Credit

Line of Credit

Series C-1 Convertible Preferred Stock

Capital Loan

Capital Loan

Capital Loan

Capital Loan

Capital Loan

Capital Loan

Capital Loan

Capital Loan

Payment

Line of Credit

Payment

Advance

Maximum

Series C-1 Convertible Preferred Stock

Initial Advance

Initial Advance

Second Advance

Second Advance

Three Month LIBOR Rate

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loan amount

'

'

'

'

'

'

'

'

$20,000,000

'

'

'

'

'

Number of advances

'

'

'

'

'

'

'

2

'

'

'

'

'

'

Proceeds from advance

12,219,000

21,404,000

'

'

'

'

'

'

'

'

12,500,000

'

'

'

Advance not yet received

'

'

'

'

'

'

'

'

'

'

'

'

7,500,000

'

Debt instrument, payment terms

'

'

'

'

'

'

'The terms of the loan require interest only payments through December 31, 2013, followed by 30 equal monthly payments of interest and principal.

'

'

'

'

'

'

'

Number of debt repayments

'

'

'

36

'

'

30

'

'

'

'

'

'

'

Final payment as a percentage of amounts borrowed

'

'

'

9.25%

'

'

6.00%

'

'

'

'

'

'

'

Debt instrument, interest rate

'

'

'

'

'

'

'

'

'

'

'

7.80%

'

'

Debt instrument, basis spread on variable rate

'

'

'

'

'

'

'

'

'

'

'

'

'

7.44%

Warrants issued to purchase preferred stock

'

'

'

'

'

6,968

'

'

'

54,437

'

'

'

'

Fair value of warrants

'

'

'

25,000

'

'

200,000

'

'

'

'

'

'

'

Warrants, fair value assumptions, interest rate

'

'

'

1.07%

'

'

1.38%

'

'

'

'

'

'

'

Warrants, fair value assumptions, expected life

'

'

'

'7 years

'

'

'7 years

'

'

'

'

'

'

'

Warrants, fair value assumptions, volatility factor

'

'

'

91.60%

'

'

91.40%

'

'

'

'

'

'

'

Warrants, fair value assumptions, dividend yield

'

'

'

0.00%

'

'

0.00%

'

'

'

'

'

'

'

Interest expense

'

'

'

40,000

'

'

400,000

'

'

'

'

'

'

'

Principal amount outstanding on loan

'

'

'

'

'

'

11,700,000

'

'

'

'

'

'

'

Line of credit amount

'

'

1,600,000

'

'

'

'

'

'

'

'

'

'

'

Line of credit, terms of repayment

'

'

'

'The terms of repayment are 36 monthly payments

'

'

'

'

'

'

'

'

'

'

Line of credit, interest rate

'

'

'

5.75%

'

'

'

'

'

'

'

'

'

'

Line of credit, utilized amount

'

'

'

'

1,300,000

'

'

'

'

'

'

'

'

'

Line of credit, remaining and expired amount

'

'

'

'

300,000

'

'

'

'

'

'

'

'

'

Line of credit, expiry date

'

'

'

30-Jun-13

'

'

'

'

'

'

'

'

'

'

Line of credit principal amount outstanding

'

'

'

$900,000

'

'

'

'

'

'

'

'

'

'

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Loss Contingencies [Line Items]	'
MOU first amendment date	27-Jun-13
MOU second amendment date	30-Sep-13
Supply agreement term	'The Supply Agreement terminates on December 31, 2020 unless terminated earlier. The Company may extend the Supply Agreement for an additional five years with notice.
Agreement termination date	31-Dec-20
Extended agreement period	'5 years
Total estimated purchase commitments	$24
Estimated payments for 2014	12.2
Estimated payments for 2015	11.8
Additional purchase commitments	$12.30

Technology_Agreement_Additiona

Technology Agreement - Additional Information (Details) (USD $)	1 Months Ended			12 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Feb. 28, 2013	Feb. 28, 2013	Feb. 28, 2013	Dec. 31, 2007	Nov. 30, 2009
		Minimum	Maximum	Series A Convertible Preferred Stock	Series A Convertible Preferred Stock
					Intellectual Property Rights
Finite Lived Intangible Assets [Line Items]	'	'	'	'	'
Shares issued during period for assets acquired	'	'	'	476,686	214,186
Shares issued during period for assets acquired, value	'	'	'	$8.20	$2
Research and development expense	12.5	'	'	'	'
Transaction cost, additional payment percentage on purchase price	'	6.70%	10.00%	'	'
Acquisition expenses	$30	'	'	'	'

Equity_Compensation_Plans_and_2

Equity Compensation Plans and Stock Based Compensation - Additional Information (Details) (USD $)	3 Months Ended			3 Months Ended			0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Nov. 30, 2013	Mar. 31, 2014
				Minimum	Maximum	2007 Equity Incentive Plan	2013 Equity Incentive Plan	2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'	'	'	'	'	'
Option granted period	'	'	'	'	'	'10 years	'10 years	'
Option vest over period	'	'	'	'	'	'4 years	'	'
Share issued or transferred under the Plan	'	'	'	'	'	'	1,276,587	'
Common stock reserved for issuance	'	'	'	'	'	'	'	1,162,902
Weighted-average grant-date fair value of options grant	$30.44	$3.78	'	'	'	'	'	'
Common stock outstanding, right of repurchase shares	3,904	'	5,125	'	'	'	'	'
Repurchase price per share	'	'	'	$3.96	$7.40	'	'	'
Per share price of aggregate intrinsic value of options	$29.81	'	'	'	'	'	'	'
Liabilities associated with shares issued with repurchase rights	$18,000	'	$23,000	'	'	'	'	'
Unrecognized compensation cost	$20,000,000	'	'	'	'	'	'	'
Expected period of compensation expense recognized	'2 years 9 months 18 days	'	'	'	'	'	'	'

Equity_Compensation_Plans_and_3

Equity Compensation Plans and Stock Based Compensation - Summary of Option Activity (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'
Shares Available for Grant, Options Outstanding, beginning balance	1,233
Shares Available for Grant, Options granted	-77
Shares Available for Grant, Restricted stock units granted	-5
Shares Available for Grant, Options exercised	'
Shares Available for Grant, Options forfeited	12
Shares Available for Grant, Options Outstanding, ending balance	1,163
Shares Subject to Outstanding Options, Options Outstanding, beginning balance	3,545
Shares Subject to Outstanding Options, Options granted	77
Shares Subject to Outstanding Options, Options exercised	'
Shares subject to Outstanding Options, Options forfeited	-12
Shares Subject to Outstanding Options, Options Outstanding, ending balance	3,610
Shares Subject to Outstanding Options, Vested and expected to vest	3,472
Shares Subject to Outstanding Options, Vested	1,301
Weighted-Average Exercise Price, Options Outstanding, beginning balance	$5.63
Weighted-Average Exercise Price, Options granted	$36.40
Weighted-Average Exercise Price, Options exercised	'
Weighted-Average Exercise Price, Options forfeited	$21.46
Weighted-Average Exercise Price, Options Outstanding, ending balance	$6.24
Weighted-Average Exercise Price, Vested and expected to vest	$6.15
Weighted-Average Exercise Price, Vested	$4.13
Weighted-Average Remaining Contractual Term, Options Outstanding	'8 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	'8 years 3 months 18 days
Weighted-Average Remaining Contractual Term, Vested	'7 years 3 months 18 days
Aggregate Intrinsic Value, Options Outstanding	$85,600
Aggregate Intrinsic Value, Vested and expected to vest	82,621
Aggregate intrinsic value, Vested	$33,400

Equity_Compensation_Plans_and_4

Equity Compensation Plans and Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Details) (USD $)	3 Months Ended		77 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'
Stock-based compensation	$1,998	$394	$9,280
Research and Development | Employees	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'
Stock-based compensation	225	144	'
Research and Development | Nonemployee Consultants	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'
Stock-based compensation	1,209	28	'
General and Administrative | Employees	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'	'
Stock-based compensation	$564	$222	'

Equity_Compensation_Plans_and_5

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Employee Stock Options (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Expected volatility	109.00%	94.70%
Expected dividends	0.00%	0.00%
Expected term (in years)	'6 years 3 months	'6 years 3 months
Risk-free rate	'	1.14%
Risk-free rate,minimum	1.84%	'
Risk-free rate,maximum	1.91%	'

Equity_Compensation_Plans_and_6

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Nonemployee Stock Options (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Expected volatility	'	81.90%
Expected dividends	0.00%	0.00%
Minimum	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Expected volatility	106.96%	'
Expected term (in years)	'6 years 1 month 6 days	'8 years 2 months 12 days
Risk-free rate	1.96%	1.47%
Maximum	'	'
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'	'
Expected volatility	122.32%	'
Expected term (in years)	'9 years 3 months 18 days	'9 years 6 months
Risk-free rate	2.59%	1.76%

Equity_Compensation_Plans_and_7

Equity Compensation Plans and Stock Based Compensation - Summary of Restricted Stock Unit Activity (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]	'
Number of Shares, Nonvested at Beginning	'
Number of Shares, Granted	5
Number of Shares, Vested	'
Number of Shares, Canceled	'
Number of Shares, Nonvested at Ending	5
Weighted Average Grant Date Fair Value Per Share, Nonvested at Beginning	'
Weighted Average Grant Date Fair Value Per Share, Granted	$32.37
Weighted Average Grant Date Fair Value Per Share, Vested	'
Weighted Average Grant Date Fair Value Per Share, Canceled	'
Weighted Average Grant Date Fair Value Per Share, Nonvested at Ending	$32.37

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Details) (USD $)	Mar. 31, 2014	Apr. 16, 2014	Apr. 30, 2014
In Millions, except Share data, unless otherwise specified		Subsequent Event	Subsequent Event
			Lease Amendment
Subsequent Event [Line Items]	'	'	'
Issuance of common stock, shares	'	4,130,611	'
Shares issued, price per share	'	$24.50	'
Aggregate net proceeds from issuance of common stock	'	$94.40	'
Public offering of common stock	4,130,611	'	'
Additional leasehold improvements	'	'	0.8
Additional leasehold including amortization	'	'	$0.20
Lease expiration date	'	'	31-Dec-19

Subsequent_Events_Schedule_of_

Subsequent Events - Schedule of Adjusted Condensed Balance Sheet Data (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheet Data:	'	'
Cash, cash equivalents and short-term investments	$78,917	$94,759
Working capital	63,117	'
Total assets	91,256	106,031
Accumulated deficit	-241,908	-225,840
Total stockholders’ equity	60,789	74,850
As Adjusted	'	'
Balance Sheet Data:	'	'
Cash, cash equivalents and short-term investments	173,345	'
Working capital	157,545	'
Total assets	185,684	'
Accumulated deficit	-241,908	'
Total stockholders’ equity	$155,217	'