Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock option exercises/deferred stock unit conversions, shares	594,231	1,319,786	206,366
Non-vested stock awards, shares	7,620	13,040	16,850
Non-vested stock units, shares	24,430	24,970	32,280
Stock Issued During Period, Shares, Acquisitions	2,000,000	0	0
Issuance of preferred stock, shares	0	6,000,000
Purchase of treasury stock, shares	18,871us-gaap_TreasuryStockSharesAcquired	2,245,572us-gaap_TreasuryStockSharesAcquired	7,960us-gaap_TreasuryStockSharesAcquired
Approximate cash dividends declared on preferred stock, per share	$ 1.34	$ 1.12
Cash dividends - common stock, per share	$ 2.03	$ 1.98	$ 1.90

Stock Units Issued During Period Shares Share Based Compensation

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- Definition

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

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

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No definition available.

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- Definition

Number of shares of stock issued during the period pursuant to acquisitions.

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- Definition

Number of new stock issued during the period.

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Number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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- Definition

Number of share options (or share units) exercised during the current period.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: 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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.28,29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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

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