Publicly traded companies are required to disclose detailed financial information so that investors can make informed decisions.
Privately held companies are not required to disclose detailed financial information, therefore most figures for private companies are only estimates. Also note public companies are not required to separately disclose financial information for their private subsidiaries, so while financial information for the subsidiary will be made available as part of the company, it may not be broken down by each subsidiary.
Mergent Online is the easiest source to use for finding company financials. It has the last 15 years or quarters available and allows easy export to Excel.
Remember that figures are most likely estimates rather than actual.
Note that Guidestar's coverage isn't complete and it doesn't provide financial information on all of the nonprofits it includes.