Earnings Per Common Share Shares Repurchase (Details) $ in Millions	Dec. 31, 2016 USD ($)
Class A Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount	$ 300.0

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.

No definition available.

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