Loss and Loss Adjustment Expense Reserves (Tables)

6 Months Ended

Jun. 30, 2018

Loss and Loss Adjustment Expenses Reserves [Abstract]

Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]

Activity in the loss and loss adjustment expense reserves is summarized as follows:

	June 30,
(millions)	2018		2017
Balance, Beginning of period	$	13,086.9	$	11,368.0
Less reinsurance recoverables on unpaid losses	2,170.1		1,801.0
Net balance, Beginning of period	10,916.8		9,567.0
Incurred related to:
Current year	10,164.6		8,804.1
Prior years	81.5		74.2
Total incurred	10,246.1		8,878.3
Paid related to:
Current year	5,533.7		4,951.0
Prior years	3,851.5		3,381.8
Total paid	9,385.2		8,332.8
Net balance, End of period	11,777.7		10,112.5
Plus reinsurance recoverables on unpaid losses	2,293.1		1,947.9
Balance, End of period	$	14,070.8	$	12,060.4