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Fair Value - Recurring Fair Value Measures (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016
Investments [Abstract] |  |  |  |  |
Cash Equivalents |  | $ 2.6 |  | $ 1.3 |
Activity in Level 3 [Roll Forward] |  |  |  |  |
U.S. Water Services Contingent Consideration, Current | [1] | 4.6 |  | 0.0 |
Recurring Fair Value Measurements [Member] |  |  |  |  |
Investments [Abstract] |  |  |  |  |
Available-for-sale – Equity Securities |  | 7.5 | [2] | 7.1 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 12.1 | [2] | 11.7 | [3]
Cash Equivalents |  | 2.6 | [2] | 1.3 | [3]
Total Fair Value of Assets |  | 22.2 |  | 20.1 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 17.2 | [4] | 16.0 | [5]
U.S. Water Services Contingent Consideration |  | 10.0 | [4] | 25.0 | [5]
Total Fair Value of Liabilities |  | 27.2 |  | 41.0 |
Total Net Fair Value of Assets (Liabilities) |  | (5.0) |  | (20.9) |
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 |  | 7.5 | [2] | 7.1 | [3]
Available-for-sale – Corporate and Governmental Debt Securities |  | 0.0 | [2] | 0.0 | [3]
Cash Equivalents |  | 2.6 | [2] | 1.3 | [3]
Total Fair Value of Assets |  | 10.1 |  | 8.4 |
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) |  | 10.1 |  | 8.4 |
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 |  | 12.1 | [2] | 11.7 | [3]
Cash Equivalents |  | 0.0 | [2] | 0.0 | [3]
Total Fair Value of Assets |  | 12.1 |  | 11.7 |
Liabilities [Abstract] |  |  |  |  |
Deferred Compensation |  | 17.2 | [4] | 16.0 | [5]
U.S. Water Services Contingent Consideration |  | 0.0 | [4] | 0.0 | [5]
Total Fair Value of Liabilities |  | 17.2 |  | 16.0 |
Total Net Fair Value of Assets (Liabilities) |  | (5.1) |  | (4.3) |
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 |  | 10.0 | [4] | 25.0 | [5]
Total Fair Value of Liabilities |  | 10.0 |  | 25.0 |
Total Net Fair Value of Assets (Liabilities) |  | (10.0) |  | (25.0) |
Activity in Level 3 [Roll Forward] |  |  |  |  |
Beginning Balance |  | 25.0 |  |  |
Ending Balance |  | 10.0 |  | $ 25.0 |
Recurring Fair Value Measurements [Member] | Level 3 [Member] | Accretion [Member] |  |  |  |  |
Activity in Level 3 [Roll Forward] |  |  |  |  |
Activity in Level 3 |  | 0.5 |  |  |
Recurring Fair Value Measurements [Member] | Level 3 [Member] | Payments [Member] |  |  |  |  |
Activity in Level 3 [Roll Forward] |  |  |  |  |
Activity in Level 3 | [6] | (15.1) |  |  |
Recurring Fair Value Measurements [Member] | Level 3 [Member] | Changes in Cash Flow Projections [Member] |  |  |  |  |
Activity in Level 3 [Roll Forward] |  |  |  |  |
Activity in Level 3 | [7] | $ (0.4) |  |  |
[1] | Contingent Consideration relates to the estimated fair value of the earnings-based payment resulting from the U.S. Water Services acquisition. (See 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 with the exception of the current portion of the U.S. Water Services Contingent Consideration which is included in Other Current Liabilities. (See Note 1. Operations and Significant Accounting Policies.)
[5] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[6] | Payments relate to retirement of U.S. Water Services former employees.
[7] | Changes in cash flow projections reflect the impact of a modification to the shareholder agreement in the first quarter of 2017 which provided participants a one-time election to sell shares at a determined price. Participants representing approximately half of the outstanding contingent consideration shares made the election, which were paid in April 2017, resulting in $4.6 million of the U.S. Water Services Contingent Consideration liability being classified in Other Current Liabilities on the Consolidated Balance Sheet. The remaining liability will be paid through the first quarter of 2019.

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