Multiemployer Plans that Provide Pension Benefits (Details) $ in Thousands									12 Months Ended
	Oct. 01, 2019 $ / h	Feb. 03, 2019 $ / h	Oct. 01, 2018 $ / h	Sep. 30, 2018	Feb. 04, 2018 $ / h	Feb. 05, 2017 $ / h	Jan. 01, 2016	Sep. 01, 2014 $ / h	Dec. 31, 2020 $ / h	Feb. 29, 2020 USD ($)	Dec. 31, 2019 $ / h	Mar. 02, 2019 USD ($)	Dec. 31, 2018 $ / h	Mar. 03, 2018 USD ($)	Dec. 31, 2017 $ / h
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										$ 22,671		$ 23,499		$ 20,979
1199 SEIU Health Care Employees Pension Fund
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										9,026		9,670		7,372
Minimum funding requirements (as a percent)				12.60%			10.76%
Southern California United Food and Commercial Workers Unions and Drug Employers Pension Fund
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										8,495		8,273		8,149
Minimum funding requirements for pharmacists (in dollars per hour) | $ / h									1.758		1.672
Minimum funding requirements for non pharmacists (in dollars per hour) | $ / h									0.797		0.758
Minimum funding requirements (in dollars per hour) | $ / h													1.586
UFCW Pharmacists, Clerks and Drug Employers Pension Trust
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										2,421		2,666		2,739
Minimum funding requirements (in dollars per hour) | $ / h								0.55
United Food and Commercial Workers Union-Employer Pension Fund
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										738		772		786
Minimum funding requirements (in dollars per hour) | $ / h		2.16			2.03	1.89
United Food and Commercial Workers Union Local 880 - Mercantile Employers Joint Pension Fund
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										437		470		495
Minimum funding requirements (in dollars per hour) | $ / h	2.06		1.97												1.88
Other Funds
Multiemployer Plans that Provide Pension Benefits
Contributions by employer										$ 1,554		$ 1,648		$ 1,438