XML 183 R31.htm IDEA: XBRL DOCUMENT
v3.10.0.1

SHARE-BASED PAYMENTS (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2018
Share-based Payments [Line Items] |
Schedule of Share-based Compensation, Restricted Stock Units Activity | The following tables set forth activity and various statistics for restricted stock unit awards outstanding under the respective plans for the period indicated:
|  | Number of Units |  | Weighted- Average Price
Nonvested at December 31, 2017 |  | 140,665 |  |  | $ | 51.97 |
Granted |  | 37,893 |  |  | $ | 68.17 |
Vested |  | (66,543 | ) |  | $ | 41.92 |
Forfeited |  | (2,509 | ) |  | $ | 62.44 |
Nonvested at December 31, 2018 |  | 109,506 |  |  | $ | 63.45 |
|  | 2018 |  | 2017 |  | 2016
Weighted-average grant date fair value (per share) |  | $ | 68.17 |  |  | $ | 63.97 |  |  | $ | 58.30 |
Fair value of shares granted (thousands of dollars) |  | $ | 2,583 |  |  | $ | 2,420 |  |  | $ | 2,503 |
Schedule of Nonvested Performance-based Units Activity | The following tables set forth activity and various statistics related to our performance stock unit awards and the assumptions used by us in the valuations of the 2018, 2017 and 2016 grants at the grant date:
|  | Number of Units |  | Weighted- Average Price
Nonvested at December 31, 2017 |  | 237,324 |  |  | $ | 57.78 |
Granted |  | 79,447 |  |  | $ | 74.04 |
Vested |  | (93,976 | ) |  | $ | 44.48 |
Forfeited |  | (3,464 | ) |  | $ | 67.97 |
Nonvested at December 31, 2018 |  | 219,331 |  |  | $ | 69.21 |
|  | 2018 |  | 2017 |  | 2016 |
Volatility (a) |  | 18.80% |  | 20.70% |  | 18.20% |
Dividend yield |  | 2.70% |  | 2.63% |  | 2.40% |
Risk-free interest rate |  | 2.38% |  | 1.48% |  | 0.91% |
(a) - Volatility based on historical volatility over three years using daily stock price observations of our peer utilities. |
|  | 2018 |  | 2017 |  | 2016
Weighted-average grant date fair value (per share) |  | $ | 74.04 |  |  | $ | 68.94 |  |  | $ | 64.06 |
Fair value of shares granted (thousands of dollars) |  | $ | 5,882 |  |  | $ | 5,110 |  |  | $ | 4,766 |

X
- Definition Tabular disclosure of the changes in outstanding nonvested performance-based units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfNonvestedPerformanceBasedUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration