v3.8.0.1

Stock Incentive Plans (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Summary Of Stock Option Activity | Option activity for the year ended December 31, 2017 is summarized below (shares in thousands):
| Shares |  | Weighted Average Exercise Price |  | Aggregate Intrinsic Value ($ in millions) |  | Weighted Average Remaining Contractual Term
Outstanding as of December 31, 2016 | 320 |  |  | $ | 17.44 |  |  |  |  |
Granted | 1 |  |  | 68.60 |  |  |  |  |
Exercised | (178 | ) |  | 13.47 |  |  |  |  |
Forfeited | (13 | ) |  | 62.86 |  |  |  |  |
Outstanding as of December 31, 2017 | 130 |  |  | $ | 18.82 |  |  | $ | 11 |  |  | 2.7
Exercisable as of December 31, 2017 | 115 |  |  | $ | 13.75 |  |  | $ | 10 |  |  | 1.9
Option Grant Pricing Assumptions | The fair value of each option grant is estimated on the date of the grant using the Black-Scholes option-pricing model with the following weighted-average assumptions:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015 (1)
Expected life (in years) | 4.8 |  | 4.8 |  | —
Risk-free interest rate | 1.9% |  | 1.6% |  | —
Expected volatility | 37.5% |  | 39.0% |  | —
Expected dividend yield | — |  | — |  | —
(1) No options were awarded in the year ended December 31, 2015.
Other Information Pertaining to Stock Option Activity | Other information pertaining to option activity is as follows:
| Year Ended December 31,
| 2017 |  | 2016 |  | 2015 (1)
Weighted-average fair value of options granted | $ | 68.60 |  |  | $ | 59.94 |  |  | $ | — |
Total intrinsic value of stock options exercised ($ in millions) | $ | 12 |  |  | $ | 19 |  |  | $ | 28 |
(1) No options were awarded in the year ended December 31, 2015.
Summary of Non-Vested Restricted Stock And Restricted Stock | A summary of the Company's non-vested restricted stock and restricted stock unit shares as of December 31, 2017, and changes during the year ended December 31, 2017, is presented below (shares in thousands):
| Shares |  | Weighted Average Grant Date Fair Value
Non-vested balance as of December 31, 2016 | 4,790 |  |  | $ | 55.75 |
Granted | 1,412 |  |  | 95.13 |
Vested | (1,883 | ) |  | 58.10 |
Forfeited | (150 | ) |  | 20.40 |
Non-vested balance as of December 31, 2017 | 4,169 |  |  | $ | 69.30 |

X
- References No definition available. + Details
Name: | us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year. + 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) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + 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 (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + 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 (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the weighted-average grant-date fair value of equity options or other equity instruments granted during the year. + 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 (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValueTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration