v2.4.0.8

Fair Value of Financial Instruments (Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | $ 69,525 | $ 94,843
After One Year through Two Years | 30,107 | 0
Over Two Years | 5,501 | 0
Fair Value | 105,133 | 94,843
Commercial paper |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 47,488 | 32,376
After One Year through Two Years | 0 | 0
Over Two Years | 0 | 0
Fair Value | 47,488 | 32,376
U.S. government agencies |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 4,004 | 62,467
After One Year through Two Years | 14,833 | 0
Over Two Years | 0 | 0
Fair Value | 18,837 | 62,467
Municipal bonds |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 1,128 |
After One Year through Two Years | 0 |
Over Two Years | 0 |
Fair Value | 1,128 |
Corporate bonds |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 16,905 |
After One Year through Two Years | 15,274 |
Over Two Years | 0 |
Fair Value | 32,179 |
Asset-backed securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Mature within One Year | 0 |
After One Year through Two Years | 0 |
Over Two Years | 5,501 |
Fair Value | $ 5,501 |

X
- Definition Available-for-sale Securities, Debt and Equity Maturities, After Year Two, Fair Value + References No definition available. + Details
Name: | qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesAfterYearTwoFairValue
Namespace Prefix: | qlys_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Available-for-sale Securities, Debt and Equity Maturities, Next Twelve Months, Fair Value + References No definition available. + Details
Name: | qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesNextTwelveMonthsFairValue
Namespace Prefix: | qlys_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Available-for-sale Securities, Debt and Equity Maturities, Year One through Two, Fair Value + References No definition available. + Details
Name: | qlys_AvailableForSaleSecuritiesDebtAndEquityMaturitiesYearOneThroughTwoFairValue
Namespace Prefix: | qlys_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration