Summary of Significant Accounting Policies - Narrative (Details) |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2018
USD ($)
segment
|
Dec. 31, 2017
USD ($)
|
|
| Summary Of Significant Accounting Policies [Line Items] | ||
| Net assets | $ 7,202,820,000 | $ 7,263,511,000 |
| Net liabilities | $ 4,034,097,000 | 3,943,902,000 |
| Number of segments | segment | 1 | |
| Reserves for uncollectible amounts | $ 11,500,000 | 12,400,000 |
| Accounts receivable | 23,800,000 | 27,200,000 |
| Reserve for losses | 1,500,000 | 1,800,000 |
| Deferred rental revenue receivables | 85,800,000 | 81,600,000 |
| Provision for income taxes | 0 | |
| Special Purpose Entity | ||
| Summary Of Significant Accounting Policies [Line Items] | ||
| Net assets | 2,840,000,000 | 2,780,000,000 |
| Net liabilities | $ 2,700,000,000 | $ 2,630,000,000 |