Cash Flow Statement - Supplemental Information - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Supplemental Cash Flow Information [Abstract]
Acquisition of net assets	$ 0.7
Deferred tax assets, net	21.1
Deferred tax liabilities, net	0.1
Deferred credits	20.3
Accounts receivable and unbilled, net	0.6
Other assets	$ 0.1

The value of an asset or business acquired in a noncash (or part noncash) acquisition. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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