Debt Commitments (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Debt Obligations and Letters of Credit Outstanding

Debt obligations and letters of credit outstanding at year end consisted of the following:

	2017			2016
Outstanding loans under unsecured revolving credit facility	$	280.0		305.0
2.00% Senior unsecured promissory note payable	40.0			40.0
2.45% Senior unsecured promissory note payable	35.0			35.0
3.22% Senior unsecured promissory note payable	60.0			—
Note payable under asset purchase agreement	—			10.0
Total debt	415.0			390.0
Less: Current portion of debt	(3.0		)	(10.5	)
Long-term debt	$	412.0		379.5
Outstanding letters of credit under unsecured revolving credit facility - contingent obligation	$	36.3		36.3