Investments in equity securities, by classification, are summarized as follows:


(in millions)	June 30, 2023		December 31, 2022
Marketable equity securities	$	430.9	$	279.5
Non-marketable equity securities		362.9		395.8
Equity method investments		73.3		78.9
	$	867.1	$	754.2

Investments in marketable equity securities are summarized as follows:


(in millions)	Cost		Unrealized losses			Estimated fair value
June 30, 2023
Common stocks	$	423.1	$	(3.7	)	$	419.4
Preferred stocks		15.6		(4.1	)		11.5
	$	438.7	$	(7.8	)	$	430.9
December 31, 2022
Common stocks	$	323.7	$	(55.6	)	$	268.1
Preferred stocks		15.3		(3.9	)		11.4
	$	339.0	$	(59.5	)	$	279.5

Net gains of $37.5 million and $49.9 million resulting from changes in the fair values of marketable equity securities were recognized for the three and six months ended June 30, 2023, respectively, which included net unrealized gains of $39.5 million and $51.2 million on securities still held at June 30, 2023, respectively. Included in net gains during the three and six months ended June 30, 2023, were unrealized gains of $25.9 million and $26.5 million, respectively, related to the Company's investment in Offerpad Solutions Inc. ("Offerpad"), a tech-enabled real estate company. Net losses of $140.5 million and $205.6 million resulting from changes in the fair values of marketable equity securities were recognized for the three and six months ended June 30, 2022, respectively, which included net unrealized losses of $133.4 million and $198.2 million on securities still held at June 30, 2022, respectively. Included in net investment losses during the three and six months ended June 30, 2022, were unrealized losses of $91.6 million and $135.6 million, respectively, related to the Company’s investment in Offerpad.

During the six months ended June 30, 2023, the Company paid $25.0 million to purchase additional shares of Offerpad common stock. The carrying amount of the Company’s investment in Offerpad at June 30, 2023 and December 31, 2022, totaled $66.3 million and $14.8 million, respectively.

Investments in non-marketable equity securities are summarized as follows:


(in millions)	Cost		Unrealized gains		Carrying amount
June 30, 2023	$	314.2	$	48.7	$	362.9
December 31, 2022	$	307.2	$	88.6	$	395.8

The Company recognized unrealized losses of $22.6 million and $39.7 million, which included impairment charges of $22.6 million and $35.5 million for the three and six months ended June 30, 2023, respectively; unrealized gains of $15.0 million during the three months ended June 30, 2022; and unrealized losses of $11.1 million during the six months ended June 30, 2022, all related to its investments in private venture-stage companies. All such unrealized losses and gains related to securities still held at June 30, 2023 and 2022.

Also, during the six months ended June 30, 2022, the Company realized a gain of $51.1 million and cash proceeds of $63.0 million related to the sale of an investment in a title insurance business.