Acquisitions - GCA Consideration Transferred (Details) - GCA Holding Corp. $ / shares in Units, shares in Millions, $ in Millions |
Sep. 01, 2017
USD ($)
$ / shares
shares
|
|---|---|
| Business Acquisition, Equity Interests Issued or Issuable [Line Items] | |
| Fair value of ABM common stock at closing | $ 421.3 |
| Cash consideration | 837.5 |
| Total consideration transferred | $ 1,258.8 |
| Common Stock | |
| Business Acquisition, Equity Interests Issued or Issuable [Line Items] | |
| Shares of ABM common stock, net of shares withheld for taxes (in shares) | shares | 9.4 |
| ABM common stock closing market price at acquisition date (usd per share) | $ / shares | $ 44.63 |