Income Taxes (Tables)

6 Months Ended

Jun. 30, 2018

Income Tax Disclosure [Abstract]

Schedule of Changes in Deferred Tax Assets

Changes to certain deferred tax assets and the valuation allowance at December 31, 2017 as a result of the Company’s expected use of tax credits to meet a portion of the transition tax were as follows (in millions):

Deferred Income Tax Assets	Estimate Refinement			Originally Reported			Change
Net operating loss tax carryovers	$	357.0		$	336.1		$	20.9
Tax credits	$	62.4		$	92.6		$	(30.2	)
Gross deferred income tax assets	$	733.6		$	742.9		$	(9.3	)
Valuation allowance	(264.7		)	(274.0		)	9.3
Total deferred income tax assets	$	468.9		$	468.9		$	—