Unisource Energy Earnings Per Share (EPS) (Details) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Numerator:
Net Income	$ 28,574	$ 25,886	$ 41,990	$ 46,032
Income from Assumed Conversion of Convertible Senior Notes	1,097	1,097	2,195	2,195
Adjusted Numerator	$ 29,671	$ 26,983	$ 44,185	$ 48,227
Weighted-average Shares of Common Stock Outstanding:
Common Shares Issued	36,757	36,106	36,676	36,006
Fully Vested Deferred Stock Units	127	121	122	114
Participating Securities	66	95	71	95
Total Weighted Average Shares of Common Stock Outstanding and Participating Securities - Basic	36,950	36,322	36,869	36,215
Effect of Dilutive Securities
Convertible Senior Notes	4,267	4,166	4,254	4,153
Options and Stock Issuable under Share Based Compensation Plans	338	412	354	446
Total Shares - Diluted	41,555	40,900	41,477	40,814
Number of stock options to purchase shares of Common Stock excluded from the computation of diluted EPS [Abstract]
Stock Options Excluded from the Diluted EPS Computation	158	229	163	232

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Numerator.

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Participating Securities.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would increase EPS amounts or decrease loss per share amounts for the period presented.

+ References

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Debt securities outstanding shall be assumed to have been converted at the beginning of the period (or at time of issuance, if later), and the resulting common shares shall be included in common shares used to calculate diluted earnings per shares. The dilutive effect of convertible debt securities shall be reflected in diluted Earnings Per Share by application of the if-converted method.

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Aggregate awards of share options and nonvested shares to be issued to an employee under a share-based compensation arrangement are considered options for purposes of computing diluted earnings per share. Such share-based awards shall be considered to be outstanding as of the grant date for purposes of computing diluted earnings per share even though their exercise may be contingent upon vesting. Those share-based awards are included in the diluted Earnings Per Share (EPS) computation even if the employee may not receive (or be able to sell) the stock until some future date. Accordingly, all shares to be issued shall be included in computing diluted EPS if the effect is dilutive. The dilutive effect of share-based compensation arrangements shall be computed using the treasury stock method. If the equity share options or other equity instruments are outstanding for only part of a period, the shares issuable shall be weighted to reflect the portion of the period during which the equity instruments were outstanding.

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In computing the dilutive effect of convertible debt, the earnings per share numerator is adjusted to add back the after-tax amount of interest recognized in the period associated with any convertible debt.

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Net Income (Loss) Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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The average number of shares issued and outstanding that are used in calculating diluted EPS, determined based on the timing of issuance of shares in the period.

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