Duration of performance evaluation for stock units to vest.

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Period (in years) from the grant date in which stock options expire.

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Percentage of performance conditions achieved.

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Length of time after vesting PSUs are required to be held.

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Quarterly value of shares available for purchase under dividend reinvestment and stock purchase plan.

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Value of annual equity awards to non employee directors.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Net number of share options (or share units) granted during the period.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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Stock Options, Restricted Stock Incentive, And Dividend Revinvestment Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grants	11,454,517
Compensation cost included in Consolidated Statements of Income for stock option and restricted stock plans	$ 17,536,000	$ 13,796,000	$ 11,351,000
Total income tax benefits recognized in income statements	$ 6,700,000	$ 5,300,000	$ 4,400,000
Stock options granted	971,328	595,229	592,551
Weighted average fair value of stock option at grant date	$ 2.95	$ 4.01	$ 3.5
Duration of performance evaluation	3 years
Parent Company [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost included in Consolidated Statements of Income for stock option and restricted stock plans	$ 16,719,000	$ 12,810,000	$ 11,351,000
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grants	8,744,702
Total grant date fair value of shares vested	$ 9,700,000	$ 9,900,000	$ 15,500,000
Employee Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost of nonvested restricted stock plans and stock options	$ 2,300,000
Recognizable weighted-average period of unrecognized compensation cost	3 years 10 months
Nonvested Restricted Stock Plans [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost of nonvested restricted stock plans and stock options	$ 26,900,000
Recognizable weighted-average period of unrecognized compensation cost	2 years 8 months
Service Condition Full Value Awards [Member] \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	4 years
Service Condition Full Value Awards [Member] \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	1 year
Performance Condition Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	3 years
Duration of performance evaluation	3 years	3 years	3 years
Performance Condition Awards [Member] \| 2013 Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of performance conditions achieved	95.80%
Performance Condition Awards [Member] \| PSUs granted after 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Post vest holding period	2 years
Market Condition Award [Member] \| 2012 Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	5 years
Market Condition Award [Member] \| 2016 Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	7 years
Director Awards [Member] \| Restricted Stock Units RSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Value of annual equity awards to non-employee directors	$ 65,000	$ 65,000
Stock Option Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted expiration	P7Y
Intrinsic value of options exercised	$ 10,600,000	$ 2,800,000	$ 400,000
Stock Option Awards [Member] \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	4 years
Stock Option Awards [Member] \| Stock Options Included In Deferral Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted expiration	P20Y
Stock Option Awards [Member] \| 2016 Units \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	6 years
Stock Option Awards [Member] \| 2016 Units \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting Period	4 years
Dividend Reinvestment Plan [Member] \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Quarterly value of shares available for purchase under dividend reinvestment and stock purchase plan	$ 10,000
Dividend Reinvestment Plan [Member] \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Quarterly value of shares available for purchase under dividend reinvestment and stock purchase plan	$ 25