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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2017
Summary of Significant Accounting Policies |
Estimated useful lives |
Asset Class | Estimated Useful Life
Buildings and land improvements | 20 – 40 years
Software | 3 – 6 years
Company vehicles | 3 – 8 years
Equipment | 6 – 10 years
Summary of award types and accounting policies |
Award Type: | Fair Value Determination | Vesting | Expense Recognition‡ | Expense Measurement
Restricted Share Awards |  |  |  |
Service Condition | Closing stock price on date of grant | Ratably; 3 or 5 years | Straight-line | Fair value at grant date
Performance Condition | Closing stock price on date of grant | Cliff; 3 years | Straight-line; Adjusted based on meeting or exceeding performance targets | Evaluated quarterly; 0 - 200% of fair value at grant date depending on performance
Market Condition | Monte-Carlo Simulation | Cliff; 3 years | Straight-line; Recognized even if condition is not met | Fair value at grant date
Stock Options† | Black-Scholes Options Pricing Model | Ratably; 3 or 5 years | Straight-line | Fair value at grant date
†Stock options expire no later than 10 years after the grant date. ‡Expense is reversed if award is forfeited prior to vesting.

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- Definition Tabular disclosure of the useful life of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. + References No definition available. + Details
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