Summary of Significant Accounting Policies - Narrative (Details) |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
|
Jun. 30, 2018
USD ($)
|
Jun. 30, 2017
USD ($)
|
Jun. 30, 2018
USD ($)
segment
|
Jun. 30, 2017
USD ($)
|
Dec. 31, 2017
USD ($)
|
|
| Summary Of Significant Accounting Policies [Line Items] | |||||
| Net assets | $ 4,909,181,000 | $ 4,909,181,000 | $ 7,263,511,000 | ||
| Net liabilities | 2,079,895,000 | $ 2,079,895,000 | 3,943,902,000 | ||
| Number of segments | segment | 1 | ||||
| Reserves for uncollectible amounts | 3,700,000 | $ 3,700,000 | 12,400,000 | ||
| Accounts receivable | 13,100,000 | 13,100,000 | 27,200,000 | ||
| Reserve for losses | 500,000 | 500,000 | 1,800,000 | ||
| Deferred rental revenue receivables | 62,800,000 | 62,800,000 | 81,600,000 | ||
| Provision for income taxes | 0 | ||||
| Goodwill impairment | 0 | $ 0 | 0 | $ 0 | |
| Special Purpose Entity | |||||
| Summary Of Significant Accounting Policies [Line Items] | |||||
| Net assets | 910,000,000 | 910,000,000 | 2,780,000,000 | ||
| Net liabilities | $ 490,000,000 | $ 490,000,000 | $ 2,630,000,000 | ||