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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Period Type:	duration

- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

+ Details

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Period Type:	duration

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

+ Details

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- Definition

Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Preferred Stock and Stockholders' Equity - Schedule of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended												12 Months Ended
	Feb. 22, 2017	Jan. 06, 2017	Jan. 08, 2016	Jan. 09, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Dividends paid per common share (USD per share)			$ 0.92	$ 0.875		$ 0.92	$ 0.92	$ 0.92		$ 0.875	$ 0.875	$ 0.875		$ 0.75	$ 0.75	$ 0.75	$ 3.68	$ 3.5	$ 2.25
Dividends declared per common share (USD per share)					$ 0.97	$ 0.92	$ 0.92	$ 0.92	$ 0.92	$ 0.875	$ 0.875	$ 0.875	$ 0.875	$ 0.75	$ 0.75	$ 0.75	$ 3.73	$ 3.545	$ 3.125
Payments of dividends			$ 17.1	$ 16.6		$ 16.7	$ 16.8	$ 17.0		$ 16.4	$ 16.6	$ 16.7		$ 14.2	$ 14.3	$ 14.3	$ 67.6	$ 66.3	$ 42.8
Subsequent Event
Class of Stock [Line Items]
Dividends declared per common share (USD per share)	$ 0.97
Payments of dividends		$ 17.5