+If format is 'oneline', there is no detail file. Each invoice has a
+header line only, with the fields:
+
+Agent number, agent name, customer number, first name, last name, address
+line 1, address line 2, city, state, zip, invoice date, invoice number,
+amount charged, amount due,
+
+and then, for each line item, three columns containing the package number,
+description, and amount.
+
+If format is 'bridgestone', there is no detail file. Each invoice has a
+header line with the following fields in a fixed-width format:
+
+Customer number (in display format), date, name (first last), company,
+address 1, address 2, city, state, zip.
+
+This is a mailing list format, and has no per-invoice fields. To avoid
+sending redundant notices, the spooling event should have a "once" or
+"once_percust_every" condition.
+