Significant Transactions - MediaAlpha (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions			12 Months Ended
	Mar. 23, 2021	Oct. 30, 2020	Dec. 31, 2022	Dec. 31, 2021
MediaAlpha
Other Significant Noncash Transactions [Line Items]
Ownership interest (as a percent)			27.10%	28.00%
Share price (in USD per share)			$ 9.95
Investment in MediaAlpha, at fair value			$ 168.6
Other Operations
Other Significant Noncash Transactions [Line Items]
Investment in MediaAlpha, at fair value			$ 168.6	$ 261.6
Secondary Offering | MediaAlpha
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	8,050
Sale of stock, price per share (in USD per share)	$ 46.00
Sale of stock, price per share net of underwriting fees (in dollars per share)	$ 44.62
MediaAlpha
Other Significant Noncash Transactions [Line Items]
Investment owned (in shares)			16,900
Fully diluted ownership interest (as a percent)			25.10%
MediaAlpha | IPO
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,600
Sale of stock, price per share (in USD per share)		$ 19.00
Sale of stock, price per share net of underwriting fees (in dollars per share)		$ 17.67
Sale of stock, consideration received in transaction		$ 63.8
Proceeds from dividends received		$ 55.0
Increase in investment owned (in dollars per share)			$ 1.00
Increase in book value per share (in dollars per share)			$ 6.60
MediaAlpha | Secondary Offering
Other Significant Noncash Transactions [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	3,600
Sale of stock, consideration received in transaction	$ 160.3