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v3.6.0.2

Investments (Summary Financial Information) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Operating revenues | $ 658 | $ 624 | $ 643
Operating income | 331 | 299 | 330
Net income | 232 | 186 | 240
Current assets | 82 | 88 |
Non-current assets | 4,340 | 3,987 |
Current liabilities | 498 | 332 |
Non-current liabilities | 2,144 | 2,052 |
WPL [Member] |  |  |
Operating revenues | 658 | 624 | 643
Operating income | 331 | 299 | 330
Net income | 234 | 202 | $ 240
Current assets | 6 | 87 |
Non-current assets | 19 | 3,977 |
Current liabilities | 3 | 332 |
Non-current liabilities | $ 7 | $ 2,052 |

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