Income Taxes - Narratives (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Current income tax expense	$ 6.2	$ 4.2
Deferred income tax benefit	12.2	$ 5.6
Tax benefit from adjustment to deferred tax liability	$ 6.2