Reinsurance (Tables)

12 Months Ended

Dec. 31, 2017

Summary Of Direct, Assumed And Ceded Premiums Written And Earned

A summary of direct, assumed and ceded premiums written and earned for the years ended December 31, 2017, 2016 and 2015 is as follows:



	2017						2016						2015
	Written			Earned			Written			Earned			Written			Earned
Direct	$	83,974.3		$	83,417.8		$	78,200.4		$	78,726.2		$	72,925.5		$	73,259.2
Assumed	274.6			274.6			217.4			217.3			221.8			221.9
Ceded	(43.7		)	(44.7		)	(79.8		)	(83.4		)	(95.8		)	(96.0		)
Net premiums	$	84,205.2		$	83,647.7		$	78,338.0		$	78,860.1		$	73,051.5		$	73,385.1
Percentage—assumed to net premiums	0.3		%	0.3		%	0.3		%	0.3		%	0.3		%	0.3		%

Summary Of Net Premiums Written And Earned By Segment

A summary of net premiums written and earned by segment (see Note 19, “Segment Information”) for the years ended December 31, 2017, 2016 and 2015 is as follows:



	2017				2016				2015
	Written		Earned		Written		Earned		Written		Earned
Reportable segments:
Commercial & Specialty Business	$	35,683.1	$	35,804.3	$	33,355.6	$	33,831.5	$	33,016.9	$	33,078.0
Government Business	48,522.1		47,843.4		44,982.4		45,028.6		40,034.6		40,307.1
Net premiums	$	84,205.2	$	83,647.7	$	78,338.0	$	78,860.1	$	73,051.5	$	73,385.1

Effect Of Reinsurance On Benefit Expense

The effect of reinsurance on benefit expense for the years ended December 31, 2017, 2016 and 2015 is as follows:



	2017			2016			2015
Direct	$	72,135.0		$	67,221.7		$	61,674.0
Assumed	216.7			184.9			192.2
Ceded	(115.5		)	(572.2		)	(749.3		)
Net benefit expense	$	72,236.2		$	66,834.4		$	61,116.9

Effect Of Reinsurance On Certain Assets And Liabilities

The effect of reinsurance on certain assets and liabilities at December 31, 2017 and 2016 is as follows:



	2017		2016
Policy liabilities, assumed	$	54.3	$	47.2
Unearned income, assumed	0.6		0.6
Premiums payable, ceded	9.3		5.2
Premiums receivable, assumed	32.9		25.9