Debt - Debt Summary (Detail) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 2.90% | 3.20% |
| Debt | $ 9,412,631 | $ 10,608,294 |
| Credit Facilities [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 1.80% | 1.00% |
| Debt | $ 317,392 | $ 35,023 |
| Senior Notes [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 3.00% | 3.30% |
| Debt | $ 6,067,277 | $ 6,417,492 |
| Term Loan [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 1.70% | 1.40% |
| Debt | $ 2,046,945 | $ 1,484,523 |
| Unsecured Other Debt [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 6.10% | 6.10% |
| Debt | $ 13,546 | $ 14,478 |
| Secured Mortgages [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 5.70% | 4.90% |
| Debt | $ 808,096 | $ 979,585 |
| Secured Mortgage Debt of Consolidated Entities [Member] | ||
| Debt Instrument [Line Items] | ||
| Weighted Average Interest Rate | 2.90% | 3.00% |
| Debt | $ 159,375 | $ 1,677,193 |