The process whose specific outcome is the progression of the pericardium over time, from its formation to the mature structure. The pericardium is a double-walled sac that contains the heart and the roots of the aorta, vena cava and the pulmonary artery. [ http://www.ncbi.nlm.nih.gov/pubmed/15138308 http://www.ncbi.nlm.nih.gov/pubmed/16376438 GOC:rph GOC:dph ]