Commitments	3 Months Ended
Mar. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS	COMMITMENTS Letters of Credit We obtained a standby letter of credit related to our South San Francisco lease with a credit limit of $0.5 million at both March 31, 2018 and December 31, 2017. We obtained standby letters of credit related to workers compensation insurance policies with a combined credit limit of $0.5 million at March 31, 2018 and $0.6 million at December 31, 2017. We obtained two standby letters of credit related to the Lease with Ascentris for a combined credit limit of $1.0 million at both March 31, 2018 and December 31, 2017. All of the letters of credit were fully collateralized by certificates of deposit. As of March 31, 2018, none of our letters of credit have been drawn upon. As part of a purchasing card program, we were required to provide collateral in the form of certificates of deposit. The collateral requirement at December 31, 2017 was $3.0 million. During the three months ended March 31, 2018 we were notified that we had been released from this collateral requirement. As of both March 31, 2018 and December 31, 2017, the certificate of deposit used to collateralize the standby letter of credit related to our South San Francisco lease was included in short-term restricted cash and investments and the certificates of deposit used to collateralize all other letters of credit and the purchase card program were included in long-term restricted cash and investments.

COMMITMENTS

Letters of Credit

We obtained a standby letter of credit related to our South San Francisco lease with a credit limit of $0.5 million at both March 31, 2018 and December 31, 2017. We obtained standby letters of credit related to workers compensation insurance policies with a combined credit limit of $0.5 million at March 31, 2018 and $0.6 million at December 31, 2017. We obtained two standby letters of credit related to the Lease with Ascentris for a combined credit limit of $1.0 million at both March 31, 2018 and December 31, 2017. All of the letters of credit were fully collateralized by certificates of deposit. As of March 31, 2018, none of our letters of credit have been drawn upon.

As part of a purchasing card program, we were required to provide collateral in the form of certificates of deposit. The collateral requirement at December 31, 2017 was $3.0 million. During the three months ended March 31, 2018 we were notified that we had been released from this collateral requirement.

As of both March 31, 2018 and December 31, 2017, the certificate of deposit used to collateralize the standby letter of credit related to our South San Francisco lease was included in short-term restricted cash and investments and the certificates of deposit used to collateralize all other letters of credit and the purchase card program were included in long-term restricted cash and investments.