Derivative and Other Fair Value Instruments - Additional Information (Details) $ in Millions	1 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($) DerivativeInstrument	Jun. 30, 2019 USD ($) DerivativeInstrument	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Unrealized gain (loss) on interest rate cash flow hedges, pretax, accumulated other comprehensive income (loss)		$ 89.8	$ 65.0
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, net	$ 25.7	$ 25.7
Forward Starting Swaps [Member]
Derivative [Line Items]
Forward starting swaps settled | DerivativeInstrument	10	10
Debt instrument, term	10 years
Proceeds from settlement of derivative instruments	$ 41.8
Public notes, face value	600.0	$ 600.0
Interest expense	0.2
Increase (decrease) in charges hedge termination activities	$ 41.6