Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Long Term Standby Purchase Commitments (Details) - USD ($)
$ in Millions |
12 Months Ended |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Long-Term Standby Purchase Commitments [Member] |
|
|
| Long-term Purchase Commitment [Line Items] |
|
|
| Guarantor Obligations, Maximum Exposure, Undiscounted |
$ 2,800.0
|
$ 2,200.0
|
| Weighted average remaining maturity, Loans underlying guarantees not held by transferor |
14 years 7 months 10 days
|
14 years 3 months 18 days
|
| Guarantee obligations issued after January 1, 2003 [Member] |
|
|
| Long-term Purchase Commitment [Line Items] |
|
|
| Guarantor Obligations, Maximum Exposure, Undiscounted |
$ 4,500.0
|
$ 3,800.0
|
| Guarantee obligations issued after January 1, 2003 [Member] | Long-Term Standby Purchase Commitments [Member] |
|
|
| Long-term Purchase Commitment [Line Items] |
|
|
| Guarantor Obligations, Current Carrying Value |
30.3
|
26.8
|
| Farm & Ranch Loans and USDA Guarantees [Member] |
|
|
| Long-term Purchase Commitment [Line Items] |
|
|
| Loans and Leases Receivable, Commitments to Purchase or Sell |
60.9
|
29.7
|
| Rural Utilities Loans [Member] |
|
|
| Long-term Purchase Commitment [Line Items] |
|
|
| Loans and Leases Receivable, Commitments to Purchase or Sell |
$ 4.0
|
$ 4.0
|