Marketable Securities Held in Trusts (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Available-for-sale securities

The estimated fair value of the investments in the RCRA Trusts is as follows:

	December 31,
	2016
	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	180.2		—		(4.3		)	175.9
Municipal bonds	180.9		—		(6.6		)	174.3
U.S. government bonds	257.4		0.1		(0.3		)	257.2
Total	$	619.7	$	0.1	$	(11.2	)	$	608.6

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

The following table shows the 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, 2016.

	December 31,
	2016
	Less than 12 months
	Fair Value		Gross Unrealized Losses
Corporate debt securities	$	163.7	$	(4.3	)
Municipal bonds	162.7		(6.6		)
U.S. government bonds	202.3		(0.3		)
Total	$	528.7	$	(11.2	)

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 ofDecember 31, 2016. 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,
	2016
Due in one year or less	$	20.7
Due after one year through five years	364.8
Due after five years through ten years	163.1
Due after ten years	58.8
Total debt securities	$	607.4