| In millions, except per share items | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 | Dec-31-10 | Dec-31-09 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Rental revenues | 280.7 | 238.1 | 209.0 | 190.6 | 171.8 | 63.3 | 28.9 | 3.0 |
| Rental revenues growth | 17.9% | 13.9% | 9.7% | 11.0% | 171.3% | 119.3% | 867.8% | |
| Expenses | | | | | | | | |
| Property operating expenses | 79.5 | 67.5 | 55.9 | 51.0 | 46.4 | 19.0 | 8.7 | 0.8 |
| Real estate taxes | 44.1 | 34.4 | 29.8 | 24.7 | 21.6 | 8.7 | 4.0 | 0.3 |
| General and administrative expenses | 24.1 | 20.8 | 15.6 | 11.4 | 10.8 | 4.6 | 4.2 | 3.2 |
| Merger-related expenses | 0.5 | 4.8 | 1.2 | 3.7 | 2.5 | 6.2 | 10.8 | 3.4 |
| Interest expense | 43.9 | 30.4 | 21.4 | 23.8 | 31.4 | 11.0 | 4.9 | 0.1 |
| Amortization of deferred financing costs | 6.1 | 4.3 | 2.5 | 1.8 | | | | |
| Depreciation and amortization | 123.6 | 102.7 | 93.3 | 84.3 | 99.7 | 36.9 | 20.1 | 2.1 |
| Total expenses | 323.6 | 264.9 | 236.3 | 218.0 | 219.0 | 92.6 | 57.9 | 12.0 |
| Interest income | 7.1 | 10.2 | 10.6 | 8.5 | 7.2 | 3.4 | 1.4 | 1.1 |
| Loss on early extinguishment of debt | 0.0 | | -0.2 | | -0.5 | | | |
| Other expense, net | 0.1 | 0.1 | 0.1 | 0.1 | -0.8 | | | |
| Loss from continuing operations before gains on sales of real estate | -35.7 | -16.3 | -16.1 | -17.5 | | | | |
| Gains on sales of real estate | 43.6 | 83.0 | 16.4 | | | | | |
| Net income (loss) | 7.9 | 66.7 | 0.3 | 32.6 | -71.0 | 189.4 | -34.6 | -8.3 |
| Net (income) loss attributable to non-redeemable noncontrolling interests | | | | 3.9 | 14.1 | 3.7 | | |
| Net income (loss) available to the Company | 9.5 | 73.8 | -6.1 | 29.7 | -12.5 | 98.6 | -34.5 | -8.1 |
| Dividends to preferred stockholders | 0.0 | 0.0 | 0.0 | 0.0 | | | | |
| Net income (loss) attributable to common stockholders | 9.5 | 73.8 | -6.1 | 29.7 | -12.5 | 98.6 | -34.6 | -8.3 |
| |
| Weighted average number of common shares outstanding - basic | 166.8 | 166.6 | 168.8 | 168.7 | 166.2 | 138.1 | 83.5 | 32.5 |
| Weighted average number of common shares outstanding - diluted | 167.6 | 167.2 | 169.0 | 168.7 | 166.2 | 138.1 | 83.5 | 32.5 |
| |
| Basic and diluted earnings (loss) per common share (in dollars per share) | | | | $0.18 | ($0.08) | $0.71 | ($0.41) | ($0.26) |
| |
| Distributions declared per common share (in dollars per share) | $0.30 | $0.30 | $0.34 | $0.35 | | | | |