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Fair Value - Recurring Fair Value Measures (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2015 | Dec. 31, 2014 | Jun. 30, 2015
Investments [Abstract] |  |  |  |  |  |  |
Cash Equivalents |  |  |  | $ 2.9 |  | $ 2.8 |
Recurring Fair Value Measurements [Member] |  |  |  |  |  |  |
Investments [Abstract] |  |  |  |  |  |  |
Available-for-sale - Equity Securities |  |  |  | 8.1 | [1] | 8.1 | [2]
Available-for-sale - Corporate Debt Securities |  |  |  | 10.8 | [1] | 11.2 | [2]
Cash Equivalents |  |  |  | 2.9 | [1] | 2.8 | [2]
Total Fair Value of Assets |  |  |  | 21.8 |  | 22.1 |
Liabilities [Abstract] |  |  |  |  |  |  |
Deferred Compensation |  |  |  | 16.2 | [3] | 16.3 | [4]
Derivatives - Interest Rate Swap |  |  |  | 0.3 | [5] | 0.1 | [6]
U.S. Water Services Contingent Consideration | [4] | $ 36.8 |  |  |  | 36.8 |
Total Fair Value of Liabilities |  |  |  | 16.5 |  | 53.2 |
Total Net Fair Value of Assets (Liabilities) |  |  |  | 5.3 |  | (31.1) |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Balance as of June 30, 2015 | [4] | 36.8 |  |  |  |  |
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 |  |  |  | 8.1 | [1] | 8.1 | [2]
Available-for-sale - Corporate Debt Securities |  |  |  | 0.0 | [1] | 0.0 | [2]
Cash Equivalents |  |  |  | 2.9 | [1] | 2.8 | [2]
Total Fair Value of Assets |  |  |  | 11.0 |  | 10.9 |
Liabilities [Abstract] |  |  |  |  |  |  |
Deferred Compensation |  |  |  | 0.0 | [3] | 0.0 | [4]
Derivatives - Interest Rate Swap |  |  |  | 0.0 | [5] | 0.0 | [6]
U.S. Water Services Contingent Consideration | [4] | 0.0 |  |  |  | 0.0 |
Total Fair Value of Liabilities |  |  |  | 0.0 |  | 0.0 |
Total Net Fair Value of Assets (Liabilities) |  |  |  | 11.0 |  | 10.9 |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Balance as of June 30, 2015 | [4] | 0.0 |  |  |  |  |
Recurring Fair Value Measurements [Member] | Level 2 [Member] |  |  |  |  |  |  |
Investments [Abstract] |  |  |  |  |  |  |
Available-for-sale - Equity Securities |  |  |  | 0.0 | [1] | 0.0 | [2]
Available-for-sale - Corporate Debt Securities |  |  |  | 10.8 | [1] | 11.2 | [2]
Cash Equivalents |  |  |  | 0.0 | [1] | 0.0 | [2]
Total Fair Value of Assets |  |  |  | 10.8 |  | 11.2 |
Liabilities [Abstract] |  |  |  |  |  |  |
Deferred Compensation |  |  |  | 16.2 | [3] | 16.3 | [4]
Derivatives - Interest Rate Swap |  |  |  | 0.3 | [5] | 0.1 | [6]
U.S. Water Services Contingent Consideration | [4] | 0.0 |  |  |  | 0.0 |
Total Fair Value of Liabilities |  |  |  | 16.5 |  | 16.4 |
Total Net Fair Value of Assets (Liabilities) |  |  |  | (5.7) |  | (5.2) |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Balance as of June 30, 2015 | [4] | 0.0 |  |  |  |  |
Recurring Fair Value Measurements [Member] | Level 3 [Member] |  |  |  |  |  |  |
Investments [Abstract] |  |  |  |  |  |  |
Available-for-sale - Equity Securities |  |  |  | 0.0 | [1] | 0.0 | [2]
Available-for-sale - Corporate Debt Securities |  |  |  | 0.0 | [1] | 0.0 | [2]
Cash Equivalents |  |  |  | 0.0 | [1] | 0.0 | [2]
Total Fair Value of Assets |  |  |  | 0.0 |  | 0.0 |
Liabilities [Abstract] |  |  |  |  |  |  |
Deferred Compensation |  |  |  | 0.0 | [3] | 0.0 | [4]
Derivatives - Interest Rate Swap |  |  |  | 0.0 | [5] | 0.0 | [6]
U.S. Water Services Contingent Consideration |  | 0.0 |  | 0.0 |  | 36.8 | [4]
Total Fair Value of Liabilities |  |  |  | 0.0 |  | 36.8 |
Total Net Fair Value of Assets (Liabilities) |  |  |  | 0.0 |  | $ (36.8) |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Balance as of December 31, 2014 |  | 0.0 |  |  |  |  |
Activity in Level 3, Period Increase |  |  |  | 0.0 |  |  |
Balance as of June 30, 2015 |  | 36.8 | [4] | $ 0.0 |  |  |
Recurring Fair Value Measurements [Member] | Level 3 [Member] | Recognition of U.S. Water Services Contingent Consideration [Member] |  |  |  |  |  |  |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Activity in Level 3, Period Increase |  | 35.7 |  |  |  |  |
Recurring Fair Value Measurements [Member] | Level 3 [Member] | Accretion Expense [Member] |  |  |  |  |  |  |
Activity in Level 3 [Roll Forward] |  |  |  |  |  |  |
Activity in Level 3, Period Increase | [7] | $ 1.1 |  |  |  |  |
[1] | Included in Other Investments on the Consolidated Balance Sheet.
[2] | Included in Other Investments on the Consolidated Balance Sheet.
[3] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[4] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[5] | Included in Current Liabilities - Other on the Consolidated Balance Sheet.
[6] | Included in Current Liabilities - Other on the Consolidated Balance Sheet.
[7] | Included in Interest Expense on the Consolidated Statement of Income.

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