Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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-Publisher FASB
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- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Number of non-option equity instruments exercised by participants.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Per share or per unit amount of equity securities issued.

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Employee Share-Based Incentive Compensation Plans (Non-Qualified Options & MediaAlpha Class B Share Awards) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Jan. 20, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2016
Share-based compensation arrangement by share-based payment award
Shares issued, price per share					$ 742
Common Stock
Share-based compensation arrangement by share-based payment award
Conversion of stock, shares converted			5,142
Chief Executive Officer \| Employee Stock Option
Share-based compensation arrangement by share-based payment award
Non-option equity instruments, exercised	125,000		40,000
Options, exercises in period, intrinsic value			$ 4.4
MediaAlpha \| Class B
Share-based compensation arrangement by share-based payment award
Expense recognized		$ 0.3		$ 6.7
Compensation cost not yet recognized		$ 0.3		$ 0.3
Minimum \| MediaAlpha \| Class B
Share-based compensation arrangement by share-based payment award
Service period				36 months
Maximum \| MediaAlpha \| Class B
Share-based compensation arrangement by share-based payment award
Service period				48 months