Commitments (Summary Of Commitments) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Commitments [Abstract]
Financing assets - Due to Expire Within One Year	$ 1,594.9
Financing assets - Due to Expire After One Year	4,669.6
Financing assets - Total Outstanding	6,264.5	$ 6,008.1
Standby letters of credit - Due to Expire Within One Year	21.2
Standby letters of credit - Due to Expire After One Year	192.1
Standby letters of credit - Total Outstanding	213.3	232.2
Other letters of credit - Due to Expire Within One Year	14.2
Other letters of credit - Total Outstanding	14.2	14.0
Deferred purchase protection agreements - Due to Expire Within One Year	2,068.1
Deferred purchase protection agreements - Total Outstanding	2,068.1	2,060.5
Guarantees, acceptances and other recourse obligations - Due to Expire Within One Year	2.1
Guarantees, acceptances and other recourse obligations - Total Outstanding	2.1	1.6
Aerospace purchase commitments - Due to Expire Within One Year	0.0
Aerospace purchase commitments - Due to Expire After One Year	0.0
Aerospace purchase commitments - Total Outstanding	0.0	8,683.5
Rail and other purchase commitments - Due to Expire Within One Year	187.8
Rail and other purchase commitments - Due to Expire After One Year	8.3
Rail and other purchase commitments - Total Outstanding	$ 196.1	$ 300.7