Zulily (ZU) 10-Q 6 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document and Entity Information	9 Months Ended
	Sep. 28, 2014	Nov. 03, 2014	Nov. 03, 2014
		Common Class A [Member]	Common Class B [Member]
Entity Information [Line Items]	'	'	'
Entity Registrant Name	'zulily, inc.	'	'
Entity Central Index Key	'0001478484	'	'
Current Fiscal Year End Date	'--12-28	'	'
Entity Filer Category	'Non-accelerated Filer	'	'
Document Type	'10-Q	'	'
Document Period End Date	28-Sep-14	'	'
Document Fiscal Year Focus	'2014	'	'
Document Fiscal Period Focus	'Q3	'	'
Amendment Flag	'false	'	'
Entity Common Stock, Shares Outstanding	'	58,512,210	66,824,168

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 28, 2014	Dec. 29, 2013
In Thousands, unless otherwise specified
CURRENT ASSETS:	'	'
Cash and cash equivalents	$291,039	$290,089
Short-term investments	53,006	18,014
Accounts receivable	12,693	5,176
Inventories	22,731	12,979
Prepaid expenses and other current assets	6,306	4,192
Deferred income taxes b Net	1,676	0
Total current assets	387,451	330,450
PROPERTY AND EQUIPMENT b Net	77,460	24,613
OTHER NON-CURRENT ASSETS	1,032	1,024
Total assets	465,943	356,087
CURRENT LIABILITIES:	'	'
Accounts payable	83,134	55,607
Accrued expenses	36,190	30,773
Deferred revenue	68,098	23,250
Total current liabilities	187,422	109,630
DEFERRED INCOME TAXES b Net	1,264	0
OTHER NON-CURRENT LIABILITIES	16,690	4,254
Total liabilities	205,376	113,884
COMMITMENTS AND CONTINGENCIES (Note 3 and Note 4)	'	'
STOCKHOLDERSb EQUITY	'	'
Preferred stock, $0.0001 par valueb2,000,000 shares authorized as of September 28, 2014 and December 29, 2013; zero shares issued and outstanding as of September 28, 2014 and December 29, 2013	0	0
Additional paid-in capital	301,712	287,385
Accumulated other comprehensive loss	-33	-58
Accumulated deficit	-41,125	-45,136
Total stockholdersb equity	260,567	242,203
Total liabilities and stockholders' equity	465,943	356,087
Class A Common Stock [Member]	'	'
STOCKHOLDERSb EQUITY	'	'
Common stock	6	1
Class B Common Stock [Member]	'	'
STOCKHOLDERSb EQUITY	'	'
Common stock	$7	$11

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parentheticals) (USD $)	Sep. 28, 2014	Dec. 29, 2013
Preferred Stock, Par Value Per Share	$0.00	$0.00
Preferred Stock, Shares Authorized (in shares)	2,000,000	2,000,000
Preferred Stock, Shares Issued (in shares)	0	0
Preferred Stock, Shares Outstanding (in shares)	0	0
Common Stock, Par Value Per Share	$0.00	'
Common Stock, Shares Authorized (in shares)	775,000,000	'
Class A Common Stock [Member]	'	'
Common Stock, Par Value Per Share	$0.00	$0.00
Common Stock, Shares Authorized (in shares)	500,000,000	500,000,000
Common Stock, Shares, Issued (in shares)	58,365,856	13,225,000
Common Stock, Shares, Outstanding (in shares)	58,365,856	13,225,000
Class B Common Stock [Member]	'	'
Common Stock, Par Value Per Share	$0.00	$0.00
Common Stock, Shares Authorized (in shares)	275,000,000	275,000,000
Common Stock, Shares, Issued (in shares)	66,888,268	110,159,235
Common Stock, Shares, Outstanding (in shares)	66,888,268	110,159,235
Common Stock, Shares Subject to Repurchase (in shares)	5,209	82,682

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Income Statement [Abstract]	'	'	'	'
NET SALES	$285,836	$166,655	$808,730	$438,676
COST OF SALES	207,147	122,154	585,350	313,660
GROSS PROFIT	78,689	44,501	223,380	125,016
OPERATING EXPENSES:	'	'	'	'
Marketing	24,878	14,651	72,245	42,707
Selling, general, and administrative	54,474	32,133	147,073	82,202
TOTAL OPERATING EXPENSES	79,352	46,784	219,318	124,909
INCOME (LOSS) FROM OPERATIONS	-663	-2,283	4,062	107
INTEREST INCOME (EXPENSE)bNet	92	22	237	86
OTHER INCOME (EXPENSE)bNet	76	10	12	-38
NET INCOME (LOSS) BEFORE PROVISION FOR INCOME TAXES	-495	-2,251	4,311	155
PROVISION FOR INCOME TAXES	300	0	300	0
NET INCOME (LOSS)	-795	-2,251	4,011	155
Net income (loss) attributable to Class A and Class B common stockholders	($795)	($4,819)	$4,011	($7,475)
Net income (loss) per share attributable to Class A and Class B common stockholders:	'	'	'	'
Basic (in dollars per share)	($0.01)	($0.09)	$0.03	($0.15)
Basic (in dollars per share)	($0.01)	($0.09)	$0.03	($0.15)
Weighted average shares outstanding used to compute net income (loss) attributable to Class A and Class B common stockholders:	'	'	'	'
Basic (in shares)	124,984,564	53,495,263	124,446,242	49,936,220
Diluted (in shares)	124,984,564	53,495,263	132,796,014	49,936,220

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net income	($795)	($2,251)	$4,011	$155
OTHER COMPREHENSIVE INCOME (LOSS):	'	'	'	'
Unrealized holding gains on available-for-sale securities	12	5	44	4
Foreign currency translation adjustment	18	45	-19	70
OTHER COMPREHENSIVE INCOME, NET	30	50	25	74
TOTAL COMPREHENSIVE INCOME (LOSS)	($765)	($2,201)	$4,036	$229

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:	'	'
Net income	$4,011	$155
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	8,878	4,257
Stock-based compensation	10,525	4,896
Excess tax benefit from stock-based compensation	-645	0
Deferred income taxes	233	0
Loss on disposal of assets	149	18
Changes in operating assets and liabilities:	'	'
Accounts receivable	-7,520	-2,448
Inventories	-9,762	-7,151
Prepaid expenses and other assets	-2,022	-1,798
Accounts payable	24,744	12,192
Accrued expenses and other liabilities	17,864	6,336
Deferred revenue	44,857	12,787
Net cash provided by operating activities	91,312	29,244
CASH FLOWS FROM INVESTING ACTIVITIES:	'	'
Capital expenditures	-58,365	-12,720
Purchases of short-term and other investments	-112,948	-18,000
Proceeds from maturity and sale of short-term and other investments	78,000	8,000
Purchases of restricted cash	0	-5,400
Proceeds from maturity of restricted cash	0	5,481
Net cash used in investing activities	-93,313	-22,639
CASH FLOWS FROM FINANCING ACTIVITIES:	'	'
Proceeds from exercise of stock options	3,136	520
Excess tax benefit from stock-based compensation	645	0
Payments of deferred offering costs	-385	0
Debt issuance costs	-412	0
Deferred initial public offering costs	0	-1,563
Net cash provided by (used in) financing activities	2,984	-1,043
Effect of exchange rate changes on cash and cash equivalents	-33	64
NET INCREASE IN CASH AND CASH EQUIVALENTS	950	5,626
CASH AND CASH EQUIVALENTSbBeginning of period	290,089	96,998
CASH AND CASH EQUIVALENTSbEnd of period	291,039	102,624
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:	'	'
Payable for capital purchases	-3,576	-564
Stock-based compensation capitalized	16	15
Vesting of early exercised shares	4	8
Deferred initial public offering cost accruals	0	326
Accretion of redeemable convertible preferred stock	$0	$7,630

Description_of_Business

Description of Business	9 Months Ended
	Sep. 28, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Description of Business	'
	Description of Business
	zulily, inc. (the “Company”, “we”, “us” or “our” ) is an online retailer offering customers a fun and entertaining shopping experience with a fresh selection of new product styles launched each day. Through the Company’s desktop sites, mobile sites and mobile applications, the Company helps its customers discover new and unique products at great values that they would likely not find elsewhere. The Company, a Delaware corporation formed in 2009, primarily conducts its buying, marketing and administrative functions in Seattle, Washington. The Company also operates a buying and studio office in Columbus, Ohio, a customer service office in Gahanna, Ohio and fulfillment centers in McCarran, Nevada and Lockbourne, Ohio.
	Zulily UK Ltd. was incorporated in the United Kingdom in October 2011 and is a wholly owned subsidiary of zulily, inc. The principal corporate offices are located in London, England.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 28, 2014
Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	Basis of Presentation—The consolidated balance sheet data as of December 29, 2013 was derived from audited financial statements. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") for unaudited condensed consolidated financial information. The financial information as of December 29, 2013 is derived from the Company's audited consolidated financial statements and notes included in Item 8 in the Company's Annual Report on Form 10-K for the fiscal year ended December 29, 2013 (the "2013 Form 10-K"), filed with the U.S. Securities and Exchange Commission on February 28, 2014. The financial information included in this Quarterly Report should be read in conjunction with management's discussion and analysis of financial condition and results of operations and the consolidated financial statements and notes included in the 2013 Form 10-K. Accordingly, we have omitted certain footnotes and other disclosures that are disclosed in the 2013 Form 10-K. The accompanying unaudited condensed consolidated financial statements reflect all adjustments consisting of normal recurring adjustments which, in the opinion of management, are necessary for a fair presentation of the Company's financial position and results of its operations, as of and for the periods presented. Operating results for the three and nine months ended September 28, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending December 28, 2014, or for any other period.
	Principles of Consolidation—The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Zulily UK Ltd. All intercompany transactions and balances are eliminated in consolidation.
	Reclassifications—Certain reclassifications have been made to the condensed consolidated financial statements in the prior period to conform to the current period presentation. Specifically, merchandise deposits are included in prepaid expenses and other current assets as of September 28, 2014 and December 29, 2013. As of December 29, 2013, we reclassified $0.5 million related to merchandise deposits to prepaid expenses and other current assets.
	Out-of-Period Correction—In the three months ended September 28, 2014, we made an out-of-period error correction to our accrual for non-expiring customer merchandise credits. Specifically, the accrual was reduced to reflect the appropriate amount owed to customers as of September 28, 2014. The net impact of the adjustment was an increase to net sales of $2.8 million and a decrease to deferred revenue of the same amount. The prior period financial statements have not been recast because the Company does not view the error as material to any previously issued financial statements.
	Fiscal Year—In 2011, the Company adopted a retail calendar whereby the fiscal year ends on the Sunday closest to December 31. Each fiscal year consists of four 13-week quarters, with one extra week added in the fourth quarter every five to six years.
	Accounting Estimates—The preparation of unaudited condensed 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 unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances, the result of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates.
	Certain Risks and Concentrations—The Company maintains the majority of its cash and cash equivalents in accounts with major financial institutions within the United States, generally in the form of demand and money market accounts. Deposits in these institutions may exceed federally insured limits. The Company has not experienced any losses on its deposits of cash and cash equivalents.
	The Company is subject to certain risks and concentrations, including dependence on third-party technology providers and hosting services, exposure to risks associated with online commerce security, consumer credit risk, and credit card fraud, as well as the interpretation of state and local laws and regulations in regards to the collection and remittance of sales and use taxes and occupancy taxes. The Company also depends upon third-party service providers for processing customer orders.
	Recent Accounting Pronouncements—In July 2013, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar tax Loss, or a Tax Credit Carryforward Exists ("ASU 2013-11"). The amendments in this update require an unrecognized tax benefit, or a portion of an unrecognized tax benefit, to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except as follows: To the extent a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction to settle any additional income taxes that would result from the disallowance of a tax position or the tax law of the applicable jurisdiction does not require the entity to use, and the entity does not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. The assessment of whether a deferred tax asset is available is based on the unrecognized tax benefit and deferred tax asset that exist at the reporting date and should be made presuming disallowance of the tax position at the reporting date. The amendments in this update do not require new recurring disclosures. For public entities, ASU 2013-11 is effective for annual and interim periods beginning after December 15, 2013. The Company adopted ASU 2013-11 in the first quarter of 2014 and it did not have a material impact on the Company's consolidated financial statements or related disclosures.
	In May 2014, the FASB issued an Accounting Standard Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The guidance is effective for annual and interim reporting periods beginning after December 15, 2016, with early adoption prohibited. We are currently evaluating the impact ASU 2014-09 will have on the Company's consolidated financial statements.

Commitments

Commitments	9 Months Ended
	Sep. 28, 2014
Commitments Disclosure [Abstract]	'
Commitments	'
	COMMITMENTS
	Fulfillment Center Leases
	In January 2014, the Company entered into a lease agreement for a fulfillment center located in McCarran, Nevada. The initial, 12-year term of the lease expires in August 2026. The Company commenced operations in the new Nevada fulfillment center in the three months ended September 28, 2014. The Company is obligated to pay approximately $1.3 million in annual base rent in the first year, which includes a free rent period of six months. Beginning in the second year, the annual base rent will be approximately $2.6 million and will increase by 1.75% each year thereafter. The Company is also obligated to pay certain operating expenses, including property management fees. As part of the agreement, the Company issued a security deposit in the form of an irrevocable standby letter of credit totaling $3.0 million which expires in 2026. The standby letter of credit may be drawn if certain conditions occur, including default on payments, losses incurred due to breach or termination of the agreement.
	In September 2014, the Company entered into a lease agreement for a fulfillment center located in Bethlehem, Pennsylvania. The initial term of the lease expires 86 months from the commencement of the lease, which will occur on the earlier of December 31, 2014 or the date the Company takes possession of the leased premises. After two (2) months of free rent, the Company will be obligated to pay approximately $3.7 million in annual base rent, which shall increase by 2% each year thereafter. The Company will also be obligated to pay certain operating expenses, including property management fees. The Company expects to begin operating the new Pennsylvania fulfillment center in mid-2015.
	Credit Facility
	In January 2014, the Company entered into a $50.0 million revolving credit facility pursuant to a Credit Agreement with certain lenders (the "Credit Agreement"). Any borrowings under the Credit Agreement mature in January 2016. The Credit Agreement includes a letter of credit sub-limit of up to $15.0 million.
	Borrowings under the Credit Agreement bear annual interest, at the Company's option, in an amount equal to (i) in the case of base rate loans, 1.50% plus the highest of (a) the Federal Funds Rate plus one-half of one percent (0.50%), (b) the prime rate, and (c) the eurodollar rate plus two percent (2.00%), or (ii) in the case of eurodollar loans, for any interest period, LIBOR plus 2.50%. An undrawn commitment fee shall be payable to the lenders in an amount equal to 0.175% times the actual daily amount by which the aggregate commitments exceed the sum of the outstanding amount of loans and the outstanding amount of letter of credit obligations, calculated on a quarterly basis in arrears.
	The Credit Agreement contains customary representations and warranties and customary affirmative and negative covenants, in each case applicable to us and our subsidiaries. The negative covenants include restrictions on, among other things, indebtedness, liens, investments, mergers, dispositions, dividends and other distributions. The Credit Agreement contains certain financial covenants that require us and our subsidiaries to, among other things, maintain a specified fixed charge coverage ratio, quick ratio and a senior leverage ratio.
	The Credit Agreement includes customary events of default, including a change of control and a cross-default on our or any subsidiary’s material indebtedness. Our obligations under the Credit Agreement are secured by substantially all of our and our subsidiaries’ assets, and the Company’s obligations under the Credit Agreement will be guaranteed by certain of our subsequently acquired or organized direct and indirect domestic subsidiaries.
	During the nine months ended September 28, 2014, the Company made no borrowings under the revolving credit facility.

Contingencies

Contingencies	9 Months Ended
	Sep. 28, 2014
Contingencies Disclosure [Abstract]	'
Contingencies	'
	CONTINGENCIES
	Legal Proceedings—In the ordinary course of business, the Company may be involved in various legal proceedings, lawsuits, disputes or claims related to, among other things, alleged infringement of third-party patents and other intellectual property rights, commercial and consumer matters, product compliance and employment matters. We have been, and may in the future be, put on notice and/or sued by third parties for alleged infringement of their proprietary rights, including patent, trademark, and copyright infringement. The outcome of any such claim or litigation is inherently uncertain. Any claims against us, whether meritorious or not, could be time-consuming, result in costly litigation, damage our reputation, require significant amounts of management time and divert significant resources. Although the Company cannot predict the outcome of any such claims or litigation, it does not believe there are currently any such claims or litigation that, if resolved unfavorably, would have a material impact on the Company's financial condition, results of operations or cash flows.
	Sales Taxes—The Company believes that the likelihood of incurring a liability as a result of sales tax nexus being asserted by certain states where it does not currently collect sales tax reaches the threshold for reasonably possible; however, the Company is unable to estimate the potential exposure.

Income_Taxes_Notes

Income Taxes (Notes)	9 Months Ended
	Sep. 28, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	INCOME TAXES
	Income Taxes—The Company's income tax expense or benefit for interim periods is determined using an estimate of the Company's annual effective tax rate, adjusted for discrete items, if any, that are taken into account in the relevant period. Each quarter the Company updates its estimate of the annual effective tax rate, and if its estimated tax rate changes, the Company makes a cumulative adjustment. The Company's 2014 annual effective tax rate is lower than the federal rate primarily due to the expected use of prior period net operating losses and R&D tax credits.
	The Company's effective tax rate was 7.0% and 0.0% for the nine months ended September 28, 2014 and September 29, 2013, respectively. The effective tax rate for the nine months ended September 28, 2014 is different from the Company's estimated annual effective tax rate primarily as a result of discrete benefits for the release of the valuation allowance and for incentive stock option disqualifying dispositions.
	In order to release the valuation allowance, the Company considered all available evidence, both positive and negative, including:
	•	the nature, frequency, and severity of cumulative financial reporting losses in recent years;
	•	the projected sustainability of recent operating profitability;
	•	the predictability of future operating profitability of the character necessary to realize the net deferred tax asset; and
	•	the carryforward periods for the net operating loss, capital loss and research and development tax credit carryforwards, including the effect of reversing taxable temporary differences.
	The Company has emerged from cumulative losses in the quarter ended September 28, 2014 and has projections of sufficient future taxable income. These two items represent significant positive evidence and as of September 28, 2014, the cumulative positive evidence outweighed the historical negative evidence regarding the likelihood that the deferred tax asset for the Company's U.S. operations will be realized. This assessment was evidenced by the Company meeting all of the above criteria, resulting in its conclusion that $3.9 million of the deferred tax asset valuation allowance for the Company's U.S. operations should be released.

Stockholders_Equity

Stockholders' Equity	9 Months Ended
	Sep. 28, 2014
Equity [Abstract]	'
Stockholders' Equity	'
	STOCKHOLDERS’ EQUITY
	Preferred Stock
	The Company has 2,000,000 shares of undesignated preferred stock authorized for future issuance. Shares of preferred stock may be issued from time to time in one or more series with rights, preferences and privileges established by the Company's board of directors.
	Common Stock
	The Company's certificate of incorporation provides for two classes of common stock: Class A common stock and Class B common stock. Each holder of Class A common stock is entitled to one vote per share and each holder of Class B common stock is entitled to ten votes per share. Each share of Class B common stock may be converted into one share of Class A common stock at the option of its holder and are automatically converted upon transfer to Class A common stock, subject to certain limited exceptions. The Company's authorized Class A and Class B common stock consists of 775,000,000 shares, all with a par value of $0.0001 per share.    In November 2013, the Company completed its initial public offering ("IPO") in which it issued and sold 7,334,125 shares of Class A common stock at a public offering price of $22.00 per share and the selling stockholders sold 5,890,875 shares of Class A common stock. The Company did not receive any proceeds from the sale of shares by the selling stockholders.
	Restricted Common Stock
	As of September 28, 2014, all 52,812,500 Class B common shares under restricted stock purchase agreements entered into with the Company's founders have fully vested. No amount of compensation expense has been recognized in connection with these shares, as they were deemed to have nominal value at the date of issuance.
	Stock-Based Compensation Expense
	A summary of option activity under the Company's equity compensation plans during the nine months ended September 28, 2014 is presented below:
							Weighted
							Average
		Number of		Weighted			Remaining
		Shares		Average			Contractual		Total
		Underlying		Exercise			Term		Intrinsic
		Options		Price			(in Years)		Value
		(in thousands, except price, shares and years)
	Outstanding at December 29, 2013	13,938,487		$	7.4		8.56		$	462,558
	Granted	638,650		41.21
	Exercised	(1,869,215	)	1.68
	Canceled	(4,605	)	6.94
	Forfeited	(388,691	)	14.51
	Outstanding at September 28, 2014	12,314,626		$	9.8		8.1		$	368,111
	Vested and expected to vest at September 28, 2014	12,065,195		$	9.63		8.09		$	362,690
	Exercisable at September 28, 2014	9,010,542		$	7.6		7.93		$	287,943
	During the fiscal year ended January 1, 2012, the Company issued 1,439,627 Class B common shares for the exercise of stock options. Of this amount, 473,958 Class B common shares were early exercised and are subject to repurchase in accordance with the provision of the Company's 2009 Equity Incentive Plan. The unvested portion of the early exercised shares as of September 28, 2014 and December 29, 2013, was 5,209 and 63,151, respectively. No repurchases of the early exercised Class B common shares have been made by the Company.
	As of September 28, 2014, total unrecognized compensation cost, adjusted for estimated forfeitures, related to unvested stock options was approximately $52.7 million and the weighted-average remaining vesting period was 4.92 years.
	The Company also grants restricted stock unit ("RSU") awards to its employees and non-employee consultants under the provisions of its 2013 Equity Plan. The fair value of an RSU is generally based on the number of awards granted and the closing price of the Company's Class A common stock on the NASDAQ Global Select Market on the date of grant or measurement. An RSU award entitles the holder to receive shares of the Company's Class A common stock as the award vests, which is generally based on length of service. The Company's unvested RSUs do not have nonforfeitable rights to dividends or dividend equivalents.
	A summary of RSU activity under the Company's 2013 Equity Plan during the nine months ended September 28, 2014 is presented below:
		Number of		Weighted
		Shares		Average
		Underlying		Grant Date
		RSUs		Fair Value
	Outstanding at December 29, 2013	—		$	—
	Granted	205,811		35.59
	Vested	(675	)	34.36
	Forfeited	(3,085	)	36.27
	Outstanding at September 28, 2014	202,051		$	35.58
	As of September 28, 2014, total unrecognized compensation cost, adjusted for estimated forfeitures, related to unvested RSUs was approximately $5.8 million and the weighted-average remaining vesting period was 4.75 years.
	The following table presents the effects of stock-based compensation on the condensed consolidated statements of operations during the periods presented:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14			29-Sep-13
		(in thousands)
	Cost of sales	$	67		$	21		$	140		$	48
	Marketing expenses	242			76			550			208
	Selling, general and administrative expenses	3,385			2,199			9,835			4,640
	Total stock-based compensation expense	$	3,694		$	2,296		$	10,525		$	4,896

Net_Income_Loss_Per_Share

Net Income (Loss) Per Share	9 Months Ended
	Sep. 28, 2014
Earnings Per Share [Abstract]	'
Net Income (Loss) Per Share	'
	NET INCOME (LOSS) PER SHARE
	Net income (loss) per common share is presented using the two-class method required for participating securities. Concurrent with the closing of the IPO in November 2013, all shares of outstanding preferred stock automatically converted into 60,621,233 shares of the Company's Class B common stock. Prior to the IPO, the Company considered preferred stock to be participating securities as the holders were entitled to receive non-cumulative dividends. Additionally, the Company considers unvested restricted common stock to be participating securities because of the holders' non-forfeitable rights to dividends, in the event dividends are declared and paid. During the three and nine months ended September 28, 2014, the Company did not consider the remaining unvested restricted common stock to be participating securities because there would be no change to the reported net income (loss) per share.
	Following the completion of the Company's IPO in November 2013, Class A and Class B common stock are the only outstanding equity in the Company. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share, on all matters that are subject to stockholder vote. Shares of Class B common stock may be converted into Class A common stock at any time at the option of the stockholder, and are automatically converted upon transfer to Class A common stock, subject to certain limited exceptions.
	Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to Class A and Class B common stockholders. Net losses are not allocated to the participating securities as holders of preferred stock and unvested restricted common stock do not have a contractual obligation to share in the losses of the Company. Undistributed earnings are calculated as net income (loss) less distributed earnings, accretion of convertible preferred stock, and current period convertible preferred stock non-cumulative dividends, whether or not declared. Basic net income (loss) per share is computed by dividing net income attributable to Class A and Class B common stockholders by the weighted-average number of shares of Class A and Class B common stock outstanding during the period.
	For the calculation of diluted net income (loss), net income attributable to Class A and Class B common stockholders for basic net income (loss) is adjusted by the effect of dilutive securities, including awards under our equity compensation plans. Diluted net income (loss) per share attributable to Class A and Class B common stockholders is computed by dividing the resulting net income (loss) attributable to Class A and Class B common stockholders by the weighted-average number of fully diluted Class A and Class B common shares outstanding.
	For the three and nine months ended September 28, 2014 and September 29, 2013, the computation of basic and diluted net income (loss) per share is presented on a combined basis for Class A and Class B common stock because the results are identical.
	The following table presents the calculation of basic and diluted net income (loss) per common share:
		Three Months Ended							Nine Months Ended
		28-Sep-14				29-Sep-13			28-Sep-14		29-Sep-13
		(in thousands, except share and per share amounts)
	Numerator
	Net income (loss)	$	(795	)		$	(2,251	)	$	4,011	$	155
	Less: Accretion of convertible redeemable preferred stock	—				(2,568		)	—		(7,630		)
	Less: Undistributed earnings attributable to participating securities	—				—			—		—
	Net income (loss) attributable to Class A and Class B common stockholders	$	(795	)		$	(4,819	)	$	4,011	$	(7,475	)
	Denominator
	Weighted average shares used to compute basic net income (loss) per Class A and Class B common share	124,984,564				53,495,263			124,446,242		49,936,220
	Effect of potentially dilutive securities:
	Stock options	—				—			8,317,778		—
	Restricted stock unit awards	—				—			31,994		—
	Weighted average shares used to compute diluted net income (loss) per Class A and Class B common share	124,984,564				53,495,263			132,796,014		49,936,220
	Net income (loss) per share attributable to Class A and Class B common stockholders—basic	$	(0.01	)		$	(0.09	)	$	0.03	$	(0.15	)
	Net income (loss) per share attributable to Class A and Class B common stockholders—diluted	$	(0.01	)		$	(0.09	)	$	0.03	$	(0.15	)
	The following have been excluded from the computation of diluted net income (loss) per share attributable to Class A and Class B common stockholders as their effect would have been antidilutive:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14		29-Sep-13
	Convertible preferred shares	—			60,497,884			—		60,497,884
	Unvested restricted common shares	—			1,471,290			—		4,804,926
	Stock options	12,314,626			13,825,873			427,701		13,825,873
	Restricted stock unit awards	202,051			—			20,938		—
	Total	12,516,677			75,795,047			448,639		79,128,683

Segment_Information

Segment Information	9 Months Ended
	Sep. 28, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	SEGMENT INFORMATION
	The Company has two reportable segments: North America and United Kingdom ("U.K."). The Company’s reportable segments have been identified based on how the Company’s chief operating decision maker manages the Company’s businesses, makes operating decisions, and evaluates operating performance. The Company’s chief operating decision maker is its chief executive officer. The Company evaluates the performance of its reportable segments based on net sales and income (loss) from operations. Income (loss) from operations represents net income (loss) before interest income (expense), net, other income (expense), net and provision for income taxes. Management does not evaluate the performance of its reportable segments using asset measures.
	North America—The North America segment consists of amounts earned from retail and services sales through the Company’s U.S.-operated sites, including sales from the sites to customers in the United States, Canada, Australia and other foreign countries.
	U.K.—The U.K. segment consists of amounts earned from retail and services sales through the Company’s U.K.-operated sites, including sales from the sites to customers in the United Kingdom and other countries in Europe.
	Certain corporate-level activities are not allocated to the U.K. segment, including costs of marketing, human resources, legal, finance and technology.
	The Company accounts for intersegment sales in accordance with the underlying transfer pricing agreement between zulily, inc. and Zulily UK Ltd.
	Information on reportable segments and reconciliation to consolidated net income before provision for income taxes is as follows:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14			29-Sep-13
		(in thousands)
	North America
	Net sales	$	281,722		$	163,726		$	796,358		$	429,891
	Operating income (loss)	916			(1,077		)	8,596			3,735
	Intersegment expense	(1,518		)	(1,205		)	(4,583		)	(3,708		)
	Total segment operating income (loss)	(602		)	(2,282		)	4,013			27
	United Kingdom
	Net sales	4,114			2,929			12,372			8,785
	Intersegment sales	1,518			1,205			4,583			3,708
	Total net sales	5,632			4,134			16,955			12,493
	Segment operating income (loss)	$	(61	)	$	(1	)	$	49		$	80
	Consolidated
	Net sales
	Total sales for reportable segments	$	287,354		$	167,860		$	813,313		$	442,384
	Elimination of intersegment sales	(1,518		)	(1,205		)	(4,583		)	(3,708		)
	Total consolidated net sales	$	285,836		$	166,655		$	808,730		$	438,676
	Net income (loss) before provision for income taxes
	Total operating income (loss) for reportable segments	$	(663	)	$	(2,283	)	$	4,062		$	107
	Interest income (expense)—net	92			22			237			86
	Other income (expense)—net	76			10			12			(38		)
	Net income (loss) before provision for income taxes	$	(495	)	$	(2,251	)	$	4,311		$	155
	The Company’s assets are primarily located in the United States. We sell similar products and services in each of our segments, and revenue from external customers for each group of similar products and services are not reported to the Company’s chief operating decision maker.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 28, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	FAIR VALUE MEASUREMENTS
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. To increase the comparability of fair value measures, the following hierarchy prioritizes the inputs to valuation methodologies used to measure fair value:
	Level 1—Quoted prices for identical assets and liabilities in active markets. The Company classifies cash equivalents as Level 1 in the fair value hierarchy. Cash equivalents are comprised of highly-liquid investments, including money market funds with original maturities of less than six months. The fair value measurement of these assets is based on quoted market prices in active markets and, therefore, these assets are recorded at fair value on a recurring basis.
	Level 2—Assets and liabilities valued based on observable market data for similar instruments, such as quoted prices for similar assets or liabilities or other inputs that are observable or can be corroborated by observable market data. The Company classifies restricted cash and short-term investments as Level 2 in the fair value hierarchy. Restricted cash is comprised of certificates of deposit funds with original maturities of less than three months. Short-term investments consist of commercial paper. The fair value measurement of these assets is based on observable market-based inputs or inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	Level 3—Unobservable inputs reflecting the Company’s assumptions, consistent with reasonably available assumptions made by other market participants. These valuations require significant judgment. The Company does not have assets classified as Level 3 in the fair value hierarchy.
	The following tables summarize the Company's assets that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 28, 2014 and December 29, 2013:
		September 28, 2014
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Cash equivalents:
	Money market funds	$	18,020	$	18,020	$	—	$	—
	Short-term investments:
	Commercial paper	53,006		—		53,006		—
	Total	$	71,026	$	18,020	$	53,006	$	—
		29-Dec-13
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Cash equivalents:
	Money market funds	$	18,019	$	18,019	$	—	$	—
	Short-term investments:
	Commercial paper	18,014		—		18,014		—
	Total	$	36,033	$	18,019	$	18,014	$	—

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 28, 2014
Accounting Policies [Abstract]	'
Principles of Consolidation	'
	The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary, Zulily UK Ltd. All intercompany transactions and balances are eliminated in consolidation.
Fiscal Year	'
	In 2011, the Company adopted a retail calendar whereby the fiscal year ends on the Sunday closest to December 31. Each fiscal year consists of four 13-week quarters, with one extra week added in the fourth quarter every five to six years.
Accounting Estimates	'
	The preparation of unaudited condensed 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 unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances, the result of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates.
Cash and Cash Equivalents	'
	The Company maintains the majority of its cash and cash equivalents in accounts with major financial institutions within the United States, generally in the form of demand and money market accounts.
Risks and Concentrations	'
	The Company is subject to certain risks and concentrations, including dependence on third-party technology providers and hosting services, exposure to risks associated with online commerce security, consumer credit risk, and credit card fraud, as well as the interpretation of state and local laws and regulations in regards to the collection and remittance of sales and use taxes and occupancy taxes. The Company also depends upon third-party service providers for processing customer orders.
Recent Accounting Pronouncements	'
	In July 2013, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar tax Loss, or a Tax Credit Carryforward Exists ("ASU 2013-11"). The amendments in this update require an unrecognized tax benefit, or a portion of an unrecognized tax benefit, to be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except as follows: To the extent a net operating loss carryforward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction to settle any additional income taxes that would result from the disallowance of a tax position or the tax law of the applicable jurisdiction does not require the entity to use, and the entity does not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. The assessment of whether a deferred tax asset is available is based on the unrecognized tax benefit and deferred tax asset that exist at the reporting date and should be made presuming disallowance of the tax position at the reporting date. The amendments in this update do not require new recurring disclosures. For public entities, ASU 2013-11 is effective for annual and interim periods beginning after December 15, 2013. The Company adopted ASU 2013-11 in the first quarter of 2014 and it did not have a material impact on the Company's consolidated financial statements or related disclosures.
	In May 2014, the FASB issued an Accounting Standard Update No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”) amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The guidance is effective for annual and interim reporting periods beginning after December 15, 2016, with early adoption prohibited. We are currently evaluating the impact ASU 2014-09 will have on the Company's consolidated financial statements.

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 28, 2014
Equity [Abstract]	'
Schedule of stock options activity	'
	A summary of option activity under the Company's equity compensation plans during the nine months ended September 28, 2014 is presented below:
							Weighted
							Average
		Number of		Weighted			Remaining
		Shares		Average			Contractual		Total
		Underlying		Exercise			Term		Intrinsic
		Options		Price			(in Years)		Value
		(in thousands, except price, shares and years)
	Outstanding at December 29, 2013	13,938,487		$	7.4		8.56		$	462,558
	Granted	638,650		41.21
	Exercised	(1,869,215	)	1.68
	Canceled	(4,605	)	6.94
	Forfeited	(388,691	)	14.51
	Outstanding at September 28, 2014	12,314,626		$	9.8		8.1		$	368,111
	Vested and expected to vest at September 28, 2014	12,065,195		$	9.63		8.09		$	362,690
	Exercisable at September 28, 2014	9,010,542		$	7.6		7.93		$	287,943
Schedule RSU Award activity	'
	A summary of RSU activity under the Company's 2013 Equity Plan during the nine months ended September 28, 2014 is presented below:
		Number of		Weighted
		Shares		Average
		Underlying		Grant Date
		RSUs		Fair Value
	Outstanding at December 29, 2013	—		$	—
	Granted	205,811		35.59
	Vested	(675	)	34.36
	Forfeited	(3,085	)	36.27
	Outstanding at September 28, 2014	202,051		$	35.58
Allocation of recognized period costs	'
	The following table presents the effects of stock-based compensation on the condensed consolidated statements of operations during the periods presented:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14			29-Sep-13
		(in thousands)
	Cost of sales	$	67		$	21		$	140		$	48
	Marketing expenses	242			76			550			208
	Selling, general and administrative expenses	3,385			2,199			9,835			4,640
	Total stock-based compensation expense	$	3,694		$	2,296		$	10,525		$	4,896

Net_Income_Loss_Per_Share_Tabl

Net Income (Loss) Per Share (Tables)	9 Months Ended
	Sep. 28, 2014
Earnings Per Share [Abstract]	'
Schedule of earnings per share calculation	'
	The following table presents the calculation of basic and diluted net income (loss) per common share:
		Three Months Ended							Nine Months Ended
		28-Sep-14				29-Sep-13			28-Sep-14		29-Sep-13
		(in thousands, except share and per share amounts)
	Numerator
	Net income (loss)	$	(795	)		$	(2,251	)	$	4,011	$	155
	Less: Accretion of convertible redeemable preferred stock	—				(2,568		)	—		(7,630		)
	Less: Undistributed earnings attributable to participating securities	—				—			—		—
	Net income (loss) attributable to Class A and Class B common stockholders	$	(795	)		$	(4,819	)	$	4,011	$	(7,475	)
	Denominator
	Weighted average shares used to compute basic net income (loss) per Class A and Class B common share	124,984,564				53,495,263			124,446,242		49,936,220
	Effect of potentially dilutive securities:
	Stock options	—				—			8,317,778		—
	Restricted stock unit awards	—				—			31,994		—
	Weighted average shares used to compute diluted net income (loss) per Class A and Class B common share	124,984,564				53,495,263			132,796,014		49,936,220
	Net income (loss) per share attributable to Class A and Class B common stockholders—basic	$	(0.01	)		$	(0.09	)	$	0.03	$	(0.15	)
	Net income (loss) per share attributable to Class A and Class B common stockholders—diluted	$	(0.01	)		$	(0.09	)	$	0.03	$	(0.15	)
Schedule of antidilutive securities excluded from computation of earnings per share	'
	The following have been excluded from the computation of diluted net income (loss) per share attributable to Class A and Class B common stockholders as their effect would have been antidilutive:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14		29-Sep-13
	Convertible preferred shares	—			60,497,884			—		60,497,884
	Unvested restricted common shares	—			1,471,290			—		4,804,926
	Stock options	12,314,626			13,825,873			427,701		13,825,873
	Restricted stock unit awards	202,051			—			20,938		—
	Total	12,516,677			75,795,047			448,639		79,128,683

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 28, 2014
Segment Reporting [Abstract]	'
Schedule of Segment Reporting Information, by Segment	'
	Information on reportable segments and reconciliation to consolidated net income before provision for income taxes is as follows:
		Three Months Ended						Nine Months Ended
		28-Sep-14			29-Sep-13			28-Sep-14			29-Sep-13
		(in thousands)
	North America
	Net sales	$	281,722		$	163,726		$	796,358		$	429,891
	Operating income (loss)	916			(1,077		)	8,596			3,735
	Intersegment expense	(1,518		)	(1,205		)	(4,583		)	(3,708		)
	Total segment operating income (loss)	(602		)	(2,282		)	4,013			27
	United Kingdom
	Net sales	4,114			2,929			12,372			8,785
	Intersegment sales	1,518			1,205			4,583			3,708
	Total net sales	5,632			4,134			16,955			12,493
	Segment operating income (loss)	$	(61	)	$	(1	)	$	49		$	80
	Consolidated
	Net sales
	Total sales for reportable segments	$	287,354		$	167,860		$	813,313		$	442,384
	Elimination of intersegment sales	(1,518		)	(1,205		)	(4,583		)	(3,708		)
	Total consolidated net sales	$	285,836		$	166,655		$	808,730		$	438,676
	Net income (loss) before provision for income taxes
	Total operating income (loss) for reportable segments	$	(663	)	$	(2,283	)	$	4,062		$	107
	Interest income (expense)—net	92			22			237			86
	Other income (expense)—net	76			10			12			(38		)
	Net income (loss) before provision for income taxes	$	(495	)	$	(2,251	)	$	4,311		$	155

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 28, 2014
Fair Value Disclosures [Abstract]	'
Fair Value, Assets Measured on Recurring Basis	'
	The following tables summarize the Company's assets that are measured at fair value on a recurring basis, by level, within the fair value hierarchy as of September 28, 2014 and December 29, 2013:
		September 28, 2014
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Cash equivalents:
	Money market funds	$	18,020	$	18,020	$	—	$	—
	Short-term investments:
	Commercial paper	53,006		—		53,006		—
	Total	$	71,026	$	18,020	$	53,006	$	—
		29-Dec-13
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Cash equivalents:
	Money market funds	$	18,019	$	18,019	$	—	$	—
	Short-term investments:
	Commercial paper	18,014		—		18,014		—
	Total	$	36,033	$	18,019	$	18,014	$	—

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013	Dec. 29, 2013
	quarter		quarter
Reclassification of merchandise deposits to prepaid expenses and other current assets	$6,306	'	$6,306	'	$4,192
Net sales	285,836	166,655	808,730	438,676	'
Deferred revenue decrease	-68,098	'	-68,098	'	-23,250
Number of quarters in fiscal year	4	'	4	'	'
Number of days in each quarter	'	'	'91 days	'	'
Number of days added to the fourth quarter every five to six years	'	'	'7 days	'	'
Restatement Adjustment [Member]	'	'	'	'	'
Reclassification of merchandise deposits to prepaid expenses and other current assets	'	'	'	'	500
Out of period correction, customer merchandise credits accrual [Member]	'	'	'	'	'
Net sales	2,800	'	'	'	'
Deferred revenue decrease	$2,800	'	$2,800	'	'

Commitments_Fulfillment_Center

Commitments - Fulfillment Center Lease (Details) (USD $)	1 Months Ended
	Jan. 31, 2014	Sep. 28, 2014
	Fulfillment Center, McCarran, Nevada [Member]	Fulfillment Center, Bethlehem, Pennsylvania [Member]
Property Subject to or Available for Operating Lease [Line Items]	'	'
Initial term of the lease	'12 years	'86 months
Annual base rent obligation, first year	$1,300,000	'
Period of free rent	'6 months	'2 months
Annual base rent obligation, second year	2,600,000	'
Percent increase in base rent after year two	1.75%	'
Security deposit	3,000,000	'
Annual base rent obligation	'	$3,700,000
Annual base rent obligation, percentage of annual increase	'	2.00%

Commitments_Credit_Facility_De

Commitments - Credit Facility (Details) (USD $)	1 Months Ended
	Jan. 31, 2014
Revolving Credit Facility [Member]	'
Line of Credit Facility [Line Items]	'
Maximum borrowing capacity	$50,000,000
Undrawn commitment fee percentage	0.18%
Letter of Credit [Member]	'
Line of Credit Facility [Line Items]	'
Maximum borrowing capacity	$15,000,000
Base Rate [Member] | Revolving Credit Facility [Member]	'
Line of Credit Facility [Line Items]	'
Stated rate	1.50%
Federal Funds Rate [Member] | Revolving Credit Facility [Member]	'
Line of Credit Facility [Line Items]	'
Basis spread on variable rate	0.50%
Eurodollar [Member] | Revolving Credit Facility [Member]	'
Line of Credit Facility [Line Items]	'
Basis spread on variable rate	2.00%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]	'
Line of Credit Facility [Line Items]	'
Basis spread on variable rate	2.50%

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 28, 2014	Sep. 28, 2014	Sep. 29, 2013
Income Tax Disclosure [Abstract]	'	'	'
Effective income tax rate	'	7.00%	0.00%
Release of deferred tax asset valuation allowance	$3.90	'	'

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	Sep. 28, 2014	Dec. 29, 2013	Sep. 28, 2014	Dec. 29, 2013	Nov. 30, 2013	Sep. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
	class		Common Class A [Member]	Common Class A [Member]	Common Class A [Member]	Common Class B [Member]	Common Class B [Member]	Common Class B [Member]
					IPO [Member]			Restricted Stock [Member]
Class of Stock [Line Items]	'	'	'	'	'	'	'	'
Preferred stock, shares authorized	2,000,000	2,000,000	'	'	'	'	'	'
Number of classes of common stock	2	'	'	'	'	'	'	'
Common Stock, voting rights	'	'	1	'	'	10	'	'
Class B to Class A conversion	'	'	'	'	'	1	'	'
Common stock, shares authorized	775,000,000	'	500,000,000	500,000,000	'	275,000,000	275,000,000	'
Common stock, par value per share	$0.00	'	$0.00	$0.00	'	$0.00	$0.00	'
Shares issued, new shares	'	'	'	'	7,334,125	'	'	'
Sale of stock, price per share	'	'	'	'	$22	'	'	'
Sale of stock, number of shares sold by stockholders	'	'	'	'	5,890,875	'	'	'
Number of shares vested	'	'	'	'	'	'	'	52,812,500

Stockholders_Equity_Stock_Opti

Stockholders' Equity (Stock Option Activity) (Details) (USD $)	9 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 28, 2014	Dec. 29, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'	'
Outstanding, Beginning Balance (in shares)	13,938,487	'
Granted (in shares)	638,650	'
Exercised (in shares)	-1,869,215	'
Canceled (in shares)	-4,605	'
Forfeited (in shares)	-388,691	'
Outstanding, Ending Balance (in shares)	12,314,626	13,938,487
Vested and expected to vest (in shares)	12,065,195	'
Exercisable (in shares)	9,010,542	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Exercise Price [Abstract]	'	'
Weighted Average Exercise Price, Outstanding, Beginning Balance (in dollars per share)	$7.40	'
Weighted Average Exercise Price, Granted (in dollars per share)	$41.21	'
Weighted Average Exercise Price, Exercised (in dollars per share)	$1.68	'
Weighted Average Exercise Price, Canceled (in dollars per share)	$6.94	'
Weighted Average Exercise Price, Forfeited (in dollars per share)	$14.51	'
Weighted Average Exercise Price, Outstanding, Ending Balance (in dollars per share)	$9.80	$7.40
Weighted Average Exercise Price, Vested and expected to vest (in dollars per share)	$9.63	'
Weighted Average Exercise Price, Exercisable (in dollars per share)	$7.60	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]	'	'
Weighted Average Remaining Contractual Term, Outstanding	'8 years 1 month 6 days	'8 years 6 months 22 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	'8 years 1 month 2 days	'
Weighted Average Remaining Contractual Term, Exercisable	'7 years 11 months 5 days	'
Total Intrinsic Value, Outstanding	$368,111	$462,558
Total Intrinsic Value, Vested and expected to vest	362,690	'
Total Intrinsic Value, Exercisable	$287,943	'

Stockholders_Equity_StockBased

Stockholders' Equity (Stock-Based Compensation Expense) (Details) (USD $)	Sep. 28, 2014	Sep. 28, 2014	Jan. 01, 2012	Sep. 28, 2014	Dec. 29, 2013
In Millions, except Share data, unless otherwise specified		Stock options [Member]	2009 Plan [Member]	2009 Plan [Member]	2009 Plan [Member]
			Stock options [Member]	Stock options [Member]	Stock options [Member]
			Common Class B [Member]	Common Class B [Member]	Common Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Shares issued for the exercise of stock options	'	'	1,439,627	'	'
Shares early exercised	'	'	473,958	'	'
Unvested portion of early exercised shares	'	'	'	5,209	63,151
Total unrecognized compensation cost	$52.70	'	'	'	'
Weighted average remaining vesting period, unvested stock options	'	'4 years 11 months 1 day	'	'	'

Stockholders_Equity_RSU_Activi

Stockholders' Equity (RSU Activity) (Details) (Restricted Stock Units (RSUs) [Member], USD $)	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 28, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Unrecognized compensation cost relating to unvested RSUs	$5.80
Weighted-average remaining vesting period of RSUs	'4 years 9 months
2013 Equity Plan	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'
Outstanding (in shares)	0
Granted (in shares)	205,811
Vested (in shares)	-675
Forfeited (in shares)	-3,085
Outstanding (in shares)	202,051
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]	'
Weighted Average Grant Date Fair Value - Outstanding (in dollars per share)	$0
Weighted Average Grant Date Fair Value - Granted (in dollars per share)	$35.59
Weighted Average Grant Date Fair Value - Vested (in dollars per share)	$34.36
Weighted Average Grant Date Fair Value - Forfeited (in dollars per share)	$36.27
Weighted Average Grant Date Fair Value - Outstanding (in dollars per share)	$35.58

Stockholders_Equity_Allocation

Stockholders' Equity (Allocation of Recognized Period Costs) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense	$3,694	$2,296	$10,525	$4,896
Cost of Sales [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense	67	21	140	48
Marketing Expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense	242	76	550	208
Selling, General and Administrative Expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Stock-based compensation expense	$3,385	$2,199	$9,835	$4,640

Net_Income_Loss_Per_Share_Deta

Net Income (Loss) Per Share (Details) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013	Nov. 30, 2013	Sep. 28, 2014	Sep. 28, 2014
					Common Class B [Member]	Common Class B [Member]	Common Class A [Member]
Class of Stock [Line Items]	'	'	'	'	'	'	'
Outstanding shares of preferred stock automatically converted to shares of Class B Common Stock, upon Closing of Initial Public Offering	'	'	'	'	60,621,233	'	'
Common Stock, voting rights	'	'	'	'	'	10	1
Calculation of Basic and Diluted Income (Loss) Per Share)	'	'	'	'	'	'	'
Net income (loss)	($795)	($2,251)	$4,011	$155	'	'	'
Less: Accretion of convertible redeemable preferred stock	0	-2,568	0	-7,630	'	'	'
Less: Undistributed earnings attributable to participating securities	0	0	0	0	'	'	'
Net income (loss) attributable to Class A and Class B common stockholders	($795)	($4,819)	$4,011	($7,475)	'	'	'
Weighted average shares used to compute basic net income (loss) per Class A and Class B common share (in shares)	124,984,564	53,495,263	124,446,242	49,936,220	'	'	'
Effect of potentially dilutive securities:	'	'	'	'	'	'	'
Stock options (in shares)	0	0	8,317,778	0	'	'	'
Unvested restricted common shares (in shares)	0	0	31,994	0	'	'	'
Weighted average shares used to compute diluted net income (loss) per Class A and Class B common share (in shares)	124,984,564	53,495,263	132,796,014	49,936,220	'	'	'
Net income (loss) per share attributable to Class A and Class B common stockholdersbbasic (in dollars per share)	($0.01)	($0.09)	$0.03	($0.15)	'	'	'
Net income (loss) per share attributable to Class A and Class B common stockholdersbdiluted (in dollars per share)	($0.01)	($0.09)	$0.03	($0.15)	'	'	'

Net_Income_Loss_Per_Share_Sche

Net Income (Loss) Per Share (Schedule of Antidilutive Securities) (Details)	3 Months Ended		9 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	12,516,677	75,795,047	448,639	79,128,683
Convertible preferred shares [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	0	60,497,884	0	60,497,884
Unvested restricted common shares [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	0	1,471,290	0	4,804,926
Stock options [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	12,314,626	13,825,873	427,701	13,825,873
Restricted stock unit awards [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive securities excluded from computation of earnings per share	202,051	0	20,938	0

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013
			Segment
Segment Reporting [Abstract]	'	'	'	'
Number of reportable segments	'	'	2	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	$285,836	$166,655	$808,730	$438,676
Operating (loss) income	-663	-2,283	4,062	107
Interest income (expense)-net	92	22	237	86
Other income (expense)-net	76	10	12	-38
Net income (loss) before provision for income taxes	-495	-2,251	4,311	155
North America [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Operating (loss) income	-602	-2,282	4,013	27
United Kingdom [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	5,632	4,134	16,955	12,493
Operating (loss) income	-61	-1	49	80
Segment Reconciling Items [Member] | North America [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	281,722	163,726	796,358	429,891
Operating (loss) income	916	-1,077	8,596	3,735
Segment Reconciling Items [Member] | United Kingdom [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	4,114	2,929	12,372	8,785
Intersegment Eliminations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	-1,518	-1,205	-4,583	-3,708
Intersegment Eliminations [Member] | North America [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Operating (loss) income	-1,518	-1,205	-4,583	-3,708
Intersegment Eliminations [Member] | United Kingdom [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	1,518	1,205	4,583	3,708
Reportable Segments [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net sales	287,354	167,860	813,313	442,384
Operating (loss) income	($663)	($2,283)	$4,062	$107

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (Fair Value, Measurements, Recurring [Member], USD $)	Sep. 28, 2014	Dec. 29, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	$71,026	$36,033
Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	18,020	18,019
Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	53,006	18,014
Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	0	0
Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	18,020	18,019
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	18,020	18,019
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	0	0
Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	53,006	18,014
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	0	0
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	53,006	18,014
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Short-term investments	$0	$0