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Commitments and Contingencies (Details) $ in Thousands, £ in Millions |  |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended |
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Jun. 27, 2018 USD ($) ft² | Feb. 12, 2018 GBP (£) ft² | Aug. 16, 2017 USD ($) ft² item | Jul. 28, 2017 USD ($) ft² | Jul. 21, 2017 USD ($) ft² | May 08, 2017 USD ($) ft² | Jul. 11, 2016 USD ($) ft² item | May 20, 2016 GBP (£) ft² floor | Jul. 15, 2015 USD ($) ft² | Feb. 24, 2015 USD ($) ft² item | Feb. 24, 2014 USD ($) ft² item | Nov. 29, 1999 USD ($) ft² | Dec. 29, 2018 USD ($) | Dec. 30, 2017 USD ($) | Dec. 31, 2016 USD ($) | Jan. 02, 2016 USD ($) | Feb. 14, 2008 ft²
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2019 |  |  |  |  |  |  |  |  |  |  |  |  | $ 13,835 |  |  |  |
2020 |  |  |  |  |  |  |  |  |  |  |  |  | 13,963 |  |  |  |
2021 |  |  |  |  |  |  |  |  |  |  |  |  | 13,914 |  |  |  |
2022 |  |  |  |  |  |  |  |  |  |  |  |  | 13,972 |  |  |  |
2023 |  |  |  |  |  |  |  |  |  |  |  |  | 14,061 |  |  |  |
Thereafter |  |  |  |  |  |  |  |  |  |  |  |  | 56,272 |  |  |  |
Rental commitments |  |  |  |  |  |  |  |  |  |  |  |  | 126,017 |  |  |  |
Rent expense |  |  |  |  |  |  |  |  |  |  |  |  | 13,200 | $ 12,100 | $ 10,400 |  |
Standby letters of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,900 |  |  |  |
Boston, Massachusetts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease area | ft² |  |  |  |  |  |  |  |  |  | 67,659 | 57,602 |  |  |  |  |  |
Number of times, lease can be renewed | item |  |  | 2 |  |  |  |  |  |  | 1 | 2 |  |  |  |  |  |
Lease extension term |  |  | 5 years |  |  |  |  |  |  | 3 years | 5 years |  |  |  |  |  |
Annual base rent | $ 1,000 |  | $ 1,900 |  |  |  |  |  |  |  | $ 2,400 |  |  |  |  |  |
Increase in annual base rent (as a percent) | 1.60% |  | 1.70% |  |  |  |  |  |  |  | 2.00% |  |  |  |  |  |
Additional lease area | ft² | 14,097 |  | 28,757 |  |  |  |  |  |  | 10,057 |  |  |  |  |  |  |
Annual fixed rent |  |  |  |  |  |  |  |  |  | $ 500 |  |  |  |  |  |  |
Rent abatement |  |  |  |  |  |  |  |  |  |  | $ 1,200 |  |  |  |  |  |
Tenant improvement allowance | $ 1,200 |  | $ 2,900 |  |  |  |  |  |  |  | 4,800 |  |  |  |  |  |
Boston, Massachusetts | Secured by letters of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of the debt |  |  |  |  |  |  |  |  |  |  | $ 1,600 |  |  |  |  |  |
Washington, D.C |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of amendments | item |  |  |  |  |  |  | 6 |  |  |  |  |  |  |  |  |  |
Lease area | ft² |  |  |  |  |  |  | 6,366 |  |  |  |  | 44,932 |  |  |  |  |
Annual base rent |  |  |  |  |  |  | $ 300 |  |  |  |  | $ 1,400 |  |  |  |  |
Increase in annual base rent (as a percent) |  |  |  |  |  |  | 2.25% |  |  |  |  | 2.00% |  |  |  |  |
Rent abatement |  |  |  |  |  |  | $ 200 |  |  |  |  |  |  |  |  |  |
Tenant improvement allowance |  |  |  |  |  |  | 500 |  |  |  |  |  |  |  |  |  |
Washington, D.C | Secured by letters of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of the debt |  |  |  |  |  |  | $ 200 |  |  |  |  |  |  |  |  |  |
New York, New York |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease area | ft² |  |  |  | 44,270 |  |  |  |  | 25,261 |  |  |  |  |  |  |  |
Annual base rent |  |  |  | $ 1,400 |  |  |  |  | $ 1,800 |  |  |  |  |  |  |  |
Additional lease area | ft² |  |  |  | 2,422 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of years of annual base rent |  |  |  | 5 years |  |  |  |  | 5 years |  |  |  |  |  |  |  |
Rent abatement |  |  |  | $ 200 |  |  |  |  |  |  |  |  |  |  |  |  |
Tenant improvement allowance |  |  |  | 200 |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in rent abatement |  |  |  | 1,400 |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in tenant improvement allowance |  |  |  | 1,600 |  |  |  |  |  |  |  |  |  |  |  |  |
New York, New York | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual base rent |  |  |  | 1,500 |  |  |  |  | $ 2,000 |  |  |  |  |  |  |  |
New York, New York | Secured by letters of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of the debt |  |  |  | $ 1,300 |  |  |  |  |  |  |  |  |  |  |  |  |
Chicago, Illinois |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease area | ft² |  |  |  |  |  | 41,642 |  |  |  |  |  |  |  |  |  |  | 36,570
Lease extension term |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |
Annual base rent |  |  |  |  |  | $ 1,100 |  |  |  |  |  |  |  |  |  | $ 1,000 |
Increase in annual base rent (as a percent) |  |  |  |  |  | 2.50% |  |  |  |  |  |  |  |  |  | 2.50% |
Rent abatement |  |  |  |  |  | $ 900 |  |  |  |  |  |  |  |  |  |  |
Tenant improvement allowance |  |  |  |  |  | $ 2,300 |  |  |  |  |  |  |  |  |  |  |
London, UK |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease area | ft² |  | 30,344 |  |  |  |  |  | 22,990 |  |  |  |  |  |  |  |  |
Number of floors available for lease | floor |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |
Annual base rent | £ |  | £ 2.1 |  |  |  |  |  | £ 1.6 |  |  |  |  |  |  |  |  |
Period after which lease rent will increase |  | 5 years |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |
Additional lease area | ft² |  | 7,354 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in annual base rent | £ |  | £ 0.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional base rent abatement and tenant improvement allowance | £ |  | 1.2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total rent incentives | £ |  | £ 4.7 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
San Francisco, CA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual base rent |  |  |  |  | $ 900 |  |  |  |  |  |  |  |  |  |  |  |
Increase in annual base rent (as a percent) |  |  |  |  | 3.00% |  |  |  |  |  |  |  |  |  |  |  |
Additional lease area | ft² |  |  |  |  | 9,206 |  |  |  |  |  |  |  |  |  |  |  |
Number of years of annual base rent |  |  |  |  | 8 years |  |  |  |  |  |  |  |  |  |  |  |
Rent abatement |  |  |  |  | $ 400 |  |  |  |  |  |  |  |  |  |  |  |
Tenant improvement allowance |  |  |  |  | 1,200 |  |  |  |  |  |  |  |  |  |  |  |
San Francisco, CA | Secured by letters of credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum Rental Commitments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of the debt |  |  |  |  | $ 100 |  |  |  |  |  |  |  |  |  |  |  |

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- Definition A valuation allowance granted to lessee and/or direct costs incurred by lessor used to prepare the leased premises for tenant's occupancy. + References No definition available. + Details
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- Definition An increase valuation allowance granted to lessee and/or direct costs incurred by lessor used to prepare the leased premises for tenant's occupancy. + References No definition available. + Details
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- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Represents the number of amendments made. + References No definition available. + Details
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- Definition Number of floors available for lease. + References No definition available. + Details
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- Definition Represents number of years of annual base rent applicable before increase in rent. + References No definition available. + Details
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- Definition This element represents the annual base payments that the lessee is obligated to make in connection with a property under the terms of an agreement classified as an operating lease. + References No definition available. + Details
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- Definition Represents the increase in annual base rent. + References No definition available. + Details
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- Definition Represents the number of times by which the lease can be renewed. + References No definition available. + Details
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- Definition Represents the percentage increase in annual base rent. + References No definition available. + Details
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- Definition Represents the additional lease area to be taken by the entity. + References No definition available. + Details
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- Definition Represents the lease area to be taken by the entity. + References No definition available. + Details
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- Definition The amount of the annual fixed rent. + References No definition available. + Details
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- Definition Amount of increase in base rent abatement. + References No definition available. + Details
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- Definition Amount of base rent abatement. + References No definition available. + Details
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- Definition Amount of base rent abatement and valuation allowance granted to lessee and/or direct costs incurred by lessor used to prepare the leased premises for tenant's occupancy. + References No definition available. + Details
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- Definition Period after which operating lease initial base rent will increase. + References No definition available. + Details
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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399 + Details
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- Definition This item represents the deferred credit for an incentive or inducement received by a lessee from a lessor, in order to motivate the lessee to enter the lease agreement, which incentive or inducement is to be recognized as a reduction of rental expense over the lease term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 55 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=77891322&loc=d3e41620-112719 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e40010-112707 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39896-112707 + Details
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- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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- Definition Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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