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Minimum Years Of Service For Eligible Employees Of Postretirement Plans

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Share Based Compensation Arrangement By Share Based Payment Award Vesting Percentage Upon One Year Anniversary Of Date Of Grant

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Shareholder Return Award Performance Measurement Period

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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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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Amount of dividends expected to be paid to holders of the underlying shares or contracted instruments over the term of the instruments life.

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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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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The highest quantity of shares an employee can purchase under the plan per period.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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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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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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Price of a single share of a number of saleable stocks of a company.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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No definition available.

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Per share or per unit amount of equity securities issued.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Stock Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended						12 Months Ended
	May. 21, 2013	Jan. 31, 2016	Jul. 31, 2015	Jan. 31, 2015	Jul. 31, 2014	Jan. 31, 2014	Jul. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of common stock price paid								85.00%
Stock options term								7 years
Restricted stock unit awards granted								1,681,000	1,870,000	2,110,000
Weighted average grant date fair value of restricted stock units granted								$ 17.36	$ 18.41	$ 16.62
Stock options granted								132,000	89,000	213,000
Weighted average grant date fair value								$ 4.43	$ 5.49	$ 6.09
Total unrecognized expense related to non-vested restricted stock unit awards and stock options								$ 44,900,000
Unrecognized expense related to non-vested restricted stock unit awards and stock options expected to be recognized over weighted average period, in years								2 years 3 months 18 days
Stock based compensation expense						$ 6,600,000		$ 30,451,000	$ 40,307,000	$ 36,612,000
Maximum percent of shares allowed to purchase								10.00%
Fair market value								$ 25,000
Maximum number of shares allowed to purchase								6,000
Common stock issued to employees			500,000	500,000	500,000	400,000	400,000
Value of common stock issued to employees per share			$ 16.40	$ 16.82	$ 16.66	$ 14.98	$ 14.94
Number of shares available for grant								10,914,000	12,443,000	14,213,000	6,414,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of common stock price paid								100.00%
Period of stock granted to employees and executive officers vest in equal annual installments								4 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Restricted stock unit awards granted								1,681,000	1,870,000	2,110,000
Restricted Stock Units \| Employees
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal annual installments								4 years
Restricted Stock Units \| Director
Share-based Compensation Arrangement by Share-based Payment Award
Period of stock granted to employees and executive officers vest in equal annual installments								1 year
Percentage of awards vesting on the first anniversary of grant date								100.00%
TSR Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Total shareholder return performance measurement period						3 years
Minimum age of retirement to be eligible for PRSUs						60 years
Minimum years of service for retirement to be eligible for PRSUs						10 years
Restricted stock unit awards granted								200,000	100,000
Weighted average grant date fair value of restricted stock units granted								$ 18.21	$ 22.06
Estimated annual dividend amount per share								0.24	0.24
Stock price								$ 18.10	$ 19.16
TSR Performance-Based Restricted Stock Units \| Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved						200.00%
TSR Performance-Based Restricted Stock Units \| Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of vesting of target shares upon performance achieved						0.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares available for grant								4,900,000
2006 Equity and Cash Compensation Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Purchase Plan to increase the number of shares issuable	10,000,000
Aggregate number of shares issuable	32,000,000
1996 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Employee Stock Purchase Plan to increase the number of shares issuable	5,000,000
Aggregate number of shares issuable	30,400,000
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Common stock issued to employees		500,000
Value of common stock issued to employees per share		$ 17.57