The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Dividends received on equity and other investments during the current period.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Investment Securities - Investment in MediaAlpha textual (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Dec. 31, 2020	Mar. 31, 2021
Secondary Offering \| Marketing Technology (MediaAlpha)
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050,000.00
Sale of stock, price per share (in USD per share)	$ 46.00	$ 19.00
Sale of stock, price per share, net of underwriting fees (in USD per share)	$ 44.62	17.67
Marketing Technology (MediaAlpha)
Subsidiary, Sale of Stock [Line Items]
Share price (in USD per share)		$ 19.00	$ 39.07	$ 35.43
Proceeds from dividends received		$ 55.0	$ 55.0
Investment owned (in shares)	16,900,000	20,500,000
Ownership interest (as a percent)	28.50%	35.00%
Fully diluted ownership interest (as a percent)	26.30%	32.30%
Investment owned, balance			$ 802.2	$ 600.2
Sale of stock, price per share, net of underwriting fees (in USD per share)		$ 17.67
Marketing Technology (MediaAlpha) \| IPO
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600,000
Sale of stock, consideration received in transaction		$ 63.8
Investment owned (in shares)		20,500,000
Marketing Technology (MediaAlpha) \| Secondary Offering
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600,000
Sale of stock, consideration received in transaction	$ 160.3
Investment owned (in shares)	16,900,000