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Stock Plans (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Employee service share based compensation aggregate disclosures [Abstract] |  |  |  |  |  |
Share based compensation cost | $ 37,000,000 |  | $ 33,000,000 |  | $ 29,000,000 |
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense | 0 |  |  |  |  |
Total unrecognized compensation cost related to share-based compensation arrangements | $ 35,000,000 |  |  |  |  |
Weighted average period of time over which unrecognized compensation cost is to be recognized | 1 year 9 months 3 days |  |  |  |  |
The remaining number of RSU's or stock options that may be issued (in shares) | 30,000,000 |  |  |  |  |
Employee stock purchase plan [Abstract] |  |  |  |  |  |
The remaining balance of shares originally authorized for issue under the employee stock purchase plan (in shares) | 9,000,000 |  |  |  |  |
The percentage of market value at which shares may be issued to participating employees (in hundredths) | 90.00% |  |  |  |  |
The number of shares issued to participants under the plan during the period | 544,000 |  | 622,000 |  | 597,000 |
The weighted average fair value of each purchase right under the employee stock purchase plan (in dollars per share) | $ 50.13 |  | $ 36.57 |  | $ 36.40 |
The discount percentage off the market value for the employee stock purchase plan (in hundredths) | 10.00% |  |  |  |  |
The aggregate cost of the discount from the market value on shares issued to employees at the end of each monthly purchase period | $ 5.57 |  | $ 4.06 |  | $ 4.04 |
Stock Compensation Plan - Board of Directors |  |  |  |  |  |
Employee service share based compensation aggregate disclosures [Abstract] |  |  |  |  |  |
Non-option equity instruments granted (in shares) | 26,000 |  | 27,000 |  | 28,000 |
Weighted average price of non-option equity instruments granted | $ 57.04 |  | $ 42.90 |  | $ 41.27 |
RSUs |  |  |  |  |  |
Employee service share based compensation aggregate disclosures [Abstract] |  |  |  |  |  |
Vesting periods for plans |  |  | 3 years |  |  |
The remaining number of RSU's or stock options that may be issued (in shares) | 22,000,000 |  |  |  |  |
Units (000) |  |  |  |  |  |
Outstanding RSU's - beginning balance (in shares) | 1,439,000 |  | 1,485,000 |  | 2,077,000 |
Granted (in shares) | 717,000 | [1] | 675,000 | [2] | 561,000 | [3]
Vested (in shares) | (806,000) |  | (665,000) |  | (1,095,000) |
Surrendered (in shares) | (56,000) |  | (56,000) |  | (58,000) |
Outstanding RSU's - ending balance (in shares) | 1,294,000 |  | 1,439,000 |  | 1,485,000 |
Wtd. Average Fair Value (per share) |  |  |  |  |  |
Weighted average grant date fair value RSU's - beginning balance (in dollars per share) | $ 36.52 |  | $ 30.17 |  | $ 16.92 |
Weighted average grant date fair value RSU's - granted (in dollars per share) | 52.73 |  | 37.29 |  | 45.80 |
Weighted average grant date fair value RSU's - vested (in dollars per share) | 30.23 |  | 23.29 |  | 13.33 |
Weighted average grant date fair value RSU's - surrendered (in dollars per share) | 43.86 |  | 36.29 |  | 25.49 |
Weighted average grant date fair value RSU's - period end (in dollars per share) | $ 45.32 |  | $ 36.52 |  | $ 30.17 |
Performance Shares |  |  |  |  |  |
Units (000) |  |  |  |  |  |
Granted (in shares) | 235,000 |  | 247,000 |  | 183,000 |
Minimum | Performance Shares |  |  |  |  |  |
Employee service share based compensation aggregate disclosures [Abstract] |  |  |  |  |  |
Percentage of PBRSUs to be granted | 0.00% |  |  |  |  |
Maximum | Performance Shares |  |  |  |  |  |
Employee service share based compensation aggregate disclosures [Abstract] |  |  |  |  |  |
Percentage of PBRSUs to be granted | 200.00% |  |  |  |  |
[1] | Includes 235 thousand PBRSUs
[2] | Includes 247 thousand PBRSUs
[3] | Includes 183 thousand PBRSUs

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- Definition This element represents the discount off the market price for each purchase right under the employee stock purchase plan. + References No definition available. + Details
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- Definition This element represents the percentage of market price at which shares may be issued to employees participating in the employee stock purchase plan. + References No definition available. + Details
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- Definition This element represents the remaining balance of shares originally authorized for issue under the employee stock purchase plan. + References No definition available. + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: 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)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of shares issued during the period as a result of an employee stock purchase plan. + References Reference 1: 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=84159872&loc=d3e21463-112644 Reference 2: 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 Reference 3: 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)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: 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 + Details
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