Nature of Operations and Summary of Significant Accounting Policies Direct Financing Leases (Details) |
12 Months Ended |
|---|---|
Dec. 31, 2016 | |
| Minimum | |
| Unguaranteed Residual Percentage Of Cost [Line Items] | |
| Unguaranteed residual percent of cost | 3.00% |
| Maximum | |
| Unguaranteed Residual Percentage Of Cost [Line Items] | |
| Unguaranteed residual percent of cost | 20.00% |