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Fair Value - Recurring Fair Value Measures (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2016 | Dec. 31, 2015
Investments [Abstract] |  |  |  |  |
Cash Equivalents |  | $ 2.0 |  | $ 2.0 |
Liabilities [Abstract] |  |  |  |  |
U.S. Water Services Contingent Consideration | [1] | 37.9 |  | 36.6 |
Recurring Fair Value Measurements [Member] |  |  |  |  |
Investments [Abstract] |  |  |  |  |
Available-for-sale – Equity Securities |  | 7.7 | [2] | 7.6 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 11.7 | [2] | 10.9 | [3]
Cash Equivalents |  | 2.0 | [2] | 2.0 | [3]
Total Fair Value of Assets |  | 21.4 |  | 20.5 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 16.0 | [4] | 16.1 | [5]
U.S. Water Services Contingent Consideration |  | 37.9 | [4] | 36.6 | [5]
Total Fair Value of Liabilities |  | 53.9 |  | 52.7 |
Total Net Fair Value of Assets (Liabilities) |  | (32.5) |  | (32.2) |
Fair Value Hierarchy Transfers, All Levels |  | 0.0 |  | 0.0 |
Recurring Fair Value Measurements [Member] | Level 1 [Member] |  |  |  |  |
Investments [Abstract] |  |  |  |  |
Available-for-sale – Equity Securities |  | 7.7 | [2] | 7.6 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 0.0 | [2] | 0.0 | [3]
Cash Equivalents |  | 2.0 | [2] | 2.0 | [3]
Total Fair Value of Assets |  | 9.7 |  | 9.6 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 0.0 | [4] | 0.0 | [5]
U.S. Water Services Contingent Consideration |  | 0.0 | [4] | 0.0 | [5]
Total Fair Value of Liabilities |  | 0.0 |  | 0.0 |
Total Net Fair Value of Assets (Liabilities) |  | 9.7 |  | 9.6 |
Recurring Fair Value Measurements [Member] | Level 2 [Member] |  |  |  |  |
Investments [Abstract] |  |  |  |  |
Available-for-sale – Equity Securities |  | 0.0 | [2] | 0.0 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 11.7 | [2] | 10.9 | [3]
Cash Equivalents |  | 0.0 | [2] | 0.0 | [3]
Total Fair Value of Assets |  | 11.7 |  | 10.9 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 16.0 | [4] | 16.1 | [5]
U.S. Water Services Contingent Consideration |  | 0.0 | [4] | 0.0 | [5]
Total Fair Value of Liabilities |  | 16.0 |  | 16.1 |
Total Net Fair Value of Assets (Liabilities) |  | (4.3) |  | (5.2) |
Recurring Fair Value Measurements [Member] | Level 3 [Member] |  |  |  |  |
Investments [Abstract] |  |  |  |  |
Available-for-sale – Equity Securities |  | 0.0 | [2] | 0.0 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 0.0 | [2] | 0.0 | [3]
Cash Equivalents |  | 0.0 | [2] | 0.0 | [3]
Total Fair Value of Assets |  | 0.0 |  | 0.0 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 0.0 | [4] | 0.0 | [5]
U.S. Water Services Contingent Consideration |  | 37.9 | [4] | 36.6 | [5]
Total Fair Value of Liabilities |  | 37.9 |  | 36.6 |
Total Net Fair Value of Assets (Liabilities) |  | $ (37.9) |  | $ (36.6) |
[1] | Contingent Consideration relates to the estimated fair value of the earnings-based payment resulting from the U.S. Water Services acquisition. (See Note 3. Acquisitions and Note 5. Fair Value.)
[2] | Included in Other Investments on the Consolidated Balance Sheet.
[3] | Included in Other Investments on the Consolidated Balance Sheet.
[4] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[5] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.

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