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Stock-Based Compensation (Tables) | 3 Months Ended
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Mar. 31, 2018
Share-based Compensation [Abstract] |
Schedule Of Stock-Based Compensation Expense | Stock-based compensation expense consisted of the following (in thousands):
| Three Months Ended March 31,
| 2018 |  | 2017
Stock options | $ | 1,072 |  |  | $ | 1,004 |
Restricted stock units | 2,041 |  |  | 1,937 |
Total | $ | 3,113 |  |  | $ | 2,941 |
Schedule Of Weighted Average Assumptions For Employee Stock Options | The following table presents the weighted average assumptions for stock options granted in the periods:
| Three Months Ended March 31,
| 2018 |  | 2017
Expected option term | 4.31 years |  | 4.34 years
Expected stock price volatility | 28.48% |  | 28.95%
Risk-free interest rate | 2.43% |  | 1.70%
Expected annual dividend yield | 1.17% |  | 1.30%
Weighted average grant date fair value | $18.10 |  | $12.73
Schedule Of Weighted Average Assumptions For Restricted Stock Units | The following table presents the weighted average assumptions for restricted stock units granted in the periods:
| Three Months Ended March 31,
| 2018 |  | 2017
Vesting period | 4.00 years |  | 3.91 years
Expected annual dividend yield | 1.16% |  | 1.31%
Estimated average grant date fair value per restricted stock unit | $71.99 |  | $52.40

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- Definition Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 + Details
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- Definition Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year. + 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 (c)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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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