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Revenue Recognition (Tables) | 12 Months Ended
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Dec. 31, 2018
Revenue from Contract with Customer [Abstract] |
Revenue Recognition Under Previous Guidance | The table below provides results for the year ended December 31, 2018 as if it had been prepared under historic accounting guidance. We included operating revenue information for the years ended December 31, 2017 and 2016 for comparability.
Year Ended December 31, (in millions) |  | 2018 |  | 2017 |  | 2016
Operating Revenues |  |  |  |  |  |
Gas Distribution |  | $ | 2,348.4 |  |  | $ | 2,063.2 |  |  | $ | 1,850.9 |
Gas Transportation |  | 1,055.2 |  |  | 1,021.5 |  |  | 964.6 |
Electric |  | 1,707.4 |  |  | 1,785.5 |  |  | 1,660.8 |
Other |  | 3.5 |  |  | 4.4 |  |  | 16.2 |
Total Operating Revenues |  | $ | 5,114.5 |  |  | $ | 4,874.6 |  |  | $ | 4,492.5 |
Disaggregation of Revenue | The table below reconciles revenue disaggregation by customer class to segment revenue as well as to revenues reflected on the Statements of Consolidated Income (Loss):
Year Ended December 31, 2018 (in millions) | Gas Distribution Operations |  | Electric Operations |  | Corporate and Other |  | Total
Customer Revenues(1) |  |  |  |  |  |  |
Residential | $ | 2,250.0 |  |  | $ | 494.7 |  |  | $ | — |  |  | $ | 2,744.7 |
Commercial | 751.9 |  |  | 492.7 |  |  | — |  |  | 1,244.6 |
Industrial | 228.0 |  |  | 613.6 |  |  | — |  |  | 841.6 |
Off-system | 92.4 |  |  | — |  |  | — |  |  | 92.4 |
Miscellaneous | 49.7 |  |  | 17.4 |  |  | 0.7 |  |  | 67.8 |
Total Customer Revenues | $ | 3,372.0 |  |  | $ | 1,618.4 |  |  | $ | 0.7 |  |  | $ | 4,991.1 |
Other Revenues | 34.4 |  |  | 89.0 |  |  | — |  |  | 123.4 |
Total Operating Revenues | $ | 3,406.4 |  |  | $ | 1,707.4 |  |  | $ | 0.7 |  |  | $ | 5,114.5 |
(1) Customer revenue amounts exclude intersegment revenues. See Note 22, "Segments of Business," for discussion of intersegment revenues.
Customer Accounts Receivable | The opening and closing balances of customer receivables for the years ended December 31, 2018 and 2017 are presented in the table below. We had no significant contract assets or liabilities during the period. Additionally, we have not incurred any significant costs to obtain or fulfill contracts.
(in millions) | Customer Accounts Receivable, Billed (less reserve)(1) |  | Customer Accounts Receivable, Unbilled (less reserve)(2)
Balance as of December 31, 2017 | $ | 477.0 |  |  | $ | 378.6 |
Balance as of December 31, 2018 | 540.5 |  |  | 349.1 |
Increase (Decrease) | $ | 63.5 |  |  | $ | (29.5 | )
(1) Customer billed receivables increased over the period due to November 2018 being colder than November 2017, leading to more gas usage included in December bills. (2) Customer unbilled receivables decreased over the period due December 2018 being warmer than December 2017, leading to less estimated gas usage

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