Supplementary Data Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Feb. 14, 2018	Feb. 10, 2017
Disclosure of Repurchase Agreements [Abstract]
Stock repurchase program, authorized amount			$ 300.0	$ 300.0
Number of shares repurchased	5.1	9.4
Aggregate cost, including fees	$ 117.1	$ 216.0
Average price per share, including fees	$ 23.03	$ 22.92
Stock repurchase program, remaining authorized repurchase amount, excluding fees	$ 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
-Publisher FASB
-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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