You don't need the bill persay. Photos of said rides hidden away safely somewhere for the adjusters works as well.
Remember it's replacement value, not what it's worth...unless it's a highly priced collectors' piece, or say a Futura Colnago...*ahem* Keith..

Claim amounts should be such that if you get cleaned out, and the insurance folks cut you a cheque you can replace what was stolen. Check the deductible amount first, as sometimes this can be more than the bike is worth.