Marketable Securities Held in Trusts (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

The estimated fair value of the investments in the RCRA Trusts is as of December 31, 2018 and December 31, 2017 are as follows:



	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Level 1
Cash and cash equivalents	$	4.0	$	—	$	—		$	4.0
Level 2
Corporate debt securities	180.8		0.3		(4.3		)	176.8
Municipal bonds	186.1		0.5		(3.4		)	183.2
U.S. government bonds	262.1		3.3		—			265.4
Total	$	633.0	$	4.1	$	(7.7	)	$	629.4

	December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Level 1
Cash and cash equivalents	$	1.2	$	—	$	—		$	1.2
Level 2
Corporate debt securities	186.1		0.4		(2.2		)	184.3
Municipal bonds	184.5		0.5		(2.7		)	182.3
U.S. government bonds	261.7		—		(4.4		)	257.3
Total	$	633.5	$	0.9	$	(9.3	)	$	625.1

Fair value of available-for-sale debt securities in an unrealized loss position

The following tables show gross unrealized losses and fair values of the RCRA Trusts’ available-for-sale securities that have been in a continuous unrealized loss position deemed to be temporary as of December 31, 2018 and December 31, 2017.



	December 31, 2018					December 31, 2017
	Less than 12 months					Less than 12 months
	Fair Value		Gross Unrealized Losses^(a)			Fair Value		Gross Unrealized Losses^(a)
Corporate debt securities	$	43.9	$	(0.6	)	$	44.3	$	(0.3	)
Municipal bonds	12.3		—			64.5		(0.5		)
U.S. government bonds	—		—			255.0		(4.4		)
Total	$	56.2	$	(0.6	)	$	363.8	$	(5.2	)

	December 31, 2018					December 31, 2017
	Greater than 12 months					Greater than 12 months
	Fair Value		Gross Unrealized Losses^(a)			Fair Value		Gross Unrealized Losses^(a)
Corporate debt securities	$	103.4	$	(3.7	)	$	100.4	$	(1.9	)
Municipal bonds	117.5		(3.4		)	83.3		(2.2		)
U.S. government bonds	—		—			—		—
Total	$	220.9	$	(7.1	)	$	183.7	$	(4.1	)

______________________________


(a)	Represents the aggregate of the gross unrealized losses that have been in a continuous unrealized loss position as of December 31, 2018 and December 31, 2017.

Schedule of maturity dates for debt securities

The following table summarizes the balance by contractual maturity of the available-for-sale debt securities invested by the RCRA Trusts as of December 31, 2018. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations before the underlying contracts mature.



	December 31, 2018
Due in one year or less	$	37.3
Due after one year through five years	148.8
Due after five years through ten years	407.0
Due after ten years	32.3
Total debt securities	$	625.4