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Benefit Plans (Tables) | 12 Months Ended
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Dec. 31, 2017
Share-based Compensation [Abstract] |
LTIP Unit Award Valuation Assumptions | The fair values of the LTIP Unit Awards at issuance were determined by a lattice-binomial option-pricing model based on Monte Carlo simulations using the following assumptions:
| Year Ended December 31, 2017 |  | Year Ended December 31, 2016
Expected dividend yield | 2.71 | % |  | 2.31 | %
Expected volatility - range used | 21.50% - 21.80% |  |  | 21.01% - 21.19% |
Expected volatility - weighted average | 21.68 | % |  | 20.92 | %
Risk-free interest rate | 0.66% - 1.58% |  |  | 0.48% - 1.43% |
Summary of Restricted Stock/Unit Award and LTIP Unit Award Transactions | Restricted stock or restricted Unit award and LTIP Unit Award transactions for the year ended December 31, 2017 are summarized as follows:
| Awards |  | Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016 | 917,532 |  |  | $ | 14.35 |
Issued | 471,744 |  |  | $ | 20.70 |
Forfeited | (8,034 | ) |  | $ | 19.61 |
Vested | (268,414 | ) |  | $ | 21.36 |
Outstanding at December 31, 2017 | 1,112,828 |  |  | $ | 15.31 |

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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
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- References No definition available. + Details
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