Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of shares repurchased	5.1	13.7	13.3
Aggregate cost, including fees	$ 117.1	$ 300.1	$ 303.3
Average price per share, including fees	$ 23.03	$ 21.97	$ 22.76
2017 Share Repurchase Program
Share repurchase program, initial authorized amount	$ 300.0
Stock repurchase program, remaining authorized repurchase amount	$ 338.4

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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