Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Net Carrying Amount of Other Intangible Assets

The following table is a summary of the net carrying amount of other intangible assets as of December 31, 2017 and 2016:



(millions)	December 31, 2017		December 31, 2016
Intangible assets subject to amortization	$	354.2	$	420.4
Indefinite-lived intangible assets¹	12.4		12.4
Total	$	366.6	$	432.8

¹Indefinite-lived intangible assets are comprised of state insurance and agent licenses. State insurance licenses were previously subject to amortization under superseded accounting guidance and have $0.6 million of accumulated amortization for both periods presented.

Intangible Assets Subject to Amortization

Intangible assets subject to amortization consisted of the following:



(millions)	December 31, 2017						December 31, 2016
Category	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Policies in force	$	256.2	$	100.7	$	155.5	$	256.2	$	64.1	$	192.1
Agency relationships	159.2		31.3		127.9		159.2		19.9		139.3
Software rights	79.1		29.4		49.7		79.1		18.8		60.3
Trade name	34.8		13.7		21.1		34.8		6.1		28.7
Total	$	529.3	$	175.1	$	354.2	$	529.3	$	108.9	$	420.4

Amortization on Intangible Assets

The estimated aggregate amortization on these intangible assets for each of the next five years as of December 31, 2017, is as follows:



(millions)
Year	Amortization Expense
2018	$	71.9
2019	66.4
2020	56.9
2021	56.6
2022	29.2