Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	na
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- Definition

The per share price of the Company's stock at which the contract holder of the freestanding contract has the right to purchase or sell the Company's stock at a future date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6445032&loc=d3e90205-114008

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=6940734&loc=d3e22047-110879

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- Definition

The number of issuer's shares to which the forward contract is indexed.

+ References

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- Definition

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.

+ References

No definition available.

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- Definition

The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

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Common Stock and Earnings Per Share - Forward Sale Agreement and Issuance of Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Feb. 04, 2015	Sep. 05, 2014	Mar. 04, 2014	Feb. 26, 2014	Dec. 31, 2016	Dec. 31, 2015
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Issued					49.6	49.1
Forward Sale Agreement [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Indexed Shares				2.8
Forward Rate Per Share				$ 48.01
Shares Issued	1.4	1.4
Proceeds from Issuance of Common Stock	$ 65.4	$ 65.0
Option to Purchase Additional Shares [Member]
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares Issued			0.4
Proceeds from Issuance of Common Stock			$ 20.2