SEGMENT INFORMATION - Assets (Details) - USD ($) $ in Thousands |
Jun. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 24,275,162 | $ 21,226,171 |
| Percentage of total assets | 100.00% | 100.00% |
| Triple-Net Leased Properties | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 9,638,035 | $ 9,176,159 |
| Percentage of total assets | 39.70% | 43.20% |
| Senior Living Operations | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 8,267,934 | $ 7,421,924 |
| Percentage of total assets | 34.00% | 35.00% |
| MOB Operations | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 5,233,638 | $ 3,526,217 |
| Percentage of total assets | 21.60% | 16.60% |
| All Other | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 1,135,555 | $ 1,101,871 |
| Percentage of total assets | 4.70% | 5.20% |