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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

+ References

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 210.5-02.28)

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-Number 210

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-Paragraph 29

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The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

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Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Name Regulation S-X (SX)

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-Paragraph 29, 30

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Stockholders' Equity (Details) (USD $)	12 Months Ended			2 Months Ended
Stockholders' Equity (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 18, 2015
Stockholders' equity
Common stock, shares authorized	153,000,000us-gaap_CommonStockSharesAuthorized	153,000,000us-gaap_CommonStockSharesAuthorized
Share repurchase activity
Shares repurchased (in shares)	1,200,000us-gaap_TreasuryStockSharesAcquired	100,000us-gaap_TreasuryStockSharesAcquired	600,000us-gaap_TreasuryStockSharesAcquired
Average price (in usd per share)	$ 204.72	$ 184.89	$ 107.44
Preferred Stock
Stockholders' equity
Preferred stock, shares authorized	5,000,000.0
Common Stock
Share repurchase activity
Shares repurchased (in shares)	1,200,000	100,000	600,000
Average price (in usd per share)	$ 204.72	$ 184.89	$ 107.44
Voting Common Stock
Stockholders' equity
Common stock, shares authorized	150,000,000
Share repurchase activity
Stock repurchase program, remaining shares authorized for repurchase	1,000,000
Class B Non-Voting Common Stock
Stockholders' equity
Common stock, shares authorized	3,000,000.0
Subsequent Event \| Common Stock
Share repurchase activity
Shares repurchased (in shares)				300,000