Stockholders' Equity	12 Months Ended
Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity On February 4, 2016, the Company's Board of Directors approved a stock repurchase program (the "Program") under which the Company may purchase up to an aggregate of $500 million of its common stock over the following 18 months period. On July 27, 2017, the Company's Board of Directors authorized an increase in the size of the Program by an additional $250 million and an extension of the Program by an additional 18 months. On November 1, 2017, the Company announced that its Board of Directors had authorized an increase in the size of the Program by an additional $350 million and on July 17, 2018, its Board of Directors authorized an additional increase of $500 million in the size of the Program. On January 23, 2019, the Company's Board of Directors authorized an increase in the size of the program by an additional $500 million, resulting in total aggregate repurchases authorized under the Program of $2.1 billion. With the increase and giving effect to the Company's $1.5 billion of previous repurchases, the Company may repurchase up to $551 million in shares of its common stock at any time prior to February 1, 2020. Any stock repurchases may be made at times and in such amounts as deemed appropriate. The timing and amount of stock repurchases, if any, will depend on a variety of factors including the stock price, market conditions, corporate and regulatory requirements, and any additional constraints related to material inside information the Company may possess. Any repurchases have been and are expected to be funded by a combination of available cash flow from the business, working capital and debt. On August 3, 2017, as part of the Program, the Company entered an Accelerated Share Repurchase ("ASR") agreement ("2017 ASR Agreement") with a third-party financial institution to repurchase $250 million of its common stock. Pursuant to the 2017 ASR Agreement, the Company delivered $250 million in cash and received 1,491,647 shares based on a stock price of $142.46 on August 7, 2017. The 2017 ASR Agreement was completed on September 7, 2017, at which time the Company received 263,012 additional shares based on a final weighted average per share purchase price during the repurchase period of $142.48. On December 14, 2018, as part of the Program, the Company entered an ASR agreement ("2018 ASR Agreement") with a third-party financial institution to repurchase $220 million of its common stock. Pursuant to the 2018 ASR Agreement, the Company delivered $220 million in cash and received 1,057,035 shares based on a stock price of $176.91 on December 14, 2018. The 2018 ASR Agreement was completed on January 29, 2019, at which time the Company received 117,751 additional shares based on a final weighted average per share purchase price during the repurchase period of $187.27. The Company accounted for the 2017 and 2018 ASR Agreements as two separate transactions: (i) as shares of reacquired common stock for the shares delivered to the Company upon effectiveness of each ASR agreement and (ii) as a forward contract indexed to the Company's common stock for the undelivered shares. The initial delivery of shares was included in treasury stock at cost and results in an immediate reduction of the outstanding shares used to calculate the weighted average common shares outstanding for basic and diluted earnings per share. The forward contracts indexed to the Company's own common stock met the criteria for equity classification, and these amounts were initially recorded in additional paid-in capital. Since the beginning of the Program, 9,025,542 shares for an aggregate purchase price of $1.5 billion have been repurchased. There were 4,911,438 common shares totaling $958.7 million, 2,854,959 common shares totaling $402.4 million and 1,259,145 common shares totaling $187.7 million repurchased under the Program during 2018, 2017 and 2016, respectively.

Stockholders' Equity

On February 4, 2016, the Company's Board of Directors approved a stock repurchase program (the "Program") under which the Company may purchase up to an aggregate of $500 million of its common stock over the following 18 months period. On July 27, 2017, the Company's Board of Directors authorized an increase in the size of the Program by an additional $250 million and an extension of the Program by an additional 18 months. On November 1, 2017, the Company announced that its Board of Directors had authorized an increase in the size of the Program by an additional $350 million and on July 17, 2018, its Board of Directors authorized an additional increase of $500 million in the size of the Program. On January 23, 2019, the Company's Board of Directors authorized an increase in the size of the program by an additional $500 million, resulting in total aggregate repurchases authorized under the Program of $2.1 billion. With the increase and giving effect to the Company's $1.5 billion of previous repurchases, the Company may repurchase up to $551 million in shares of its common stock at any time prior to February 1, 2020.

Any stock repurchases may be made at times and in such amounts as deemed appropriate. The timing and amount of stock repurchases, if any, will depend on a variety of factors including the stock price, market conditions, corporate and regulatory requirements, and any additional constraints related to material inside information the Company may possess. Any repurchases have been and are expected to be funded by a combination of available cash flow from the business, working capital and debt.

On August 3, 2017, as part of the Program, the Company entered an Accelerated Share Repurchase ("ASR") agreement ("2017 ASR Agreement") with a third-party financial institution to repurchase $250 million of its common stock. Pursuant to the 2017 ASR Agreement, the Company delivered $250 million in cash and received 1,491,647 shares based on a stock price of $142.46 on August 7, 2017. The 2017 ASR Agreement was completed on September 7, 2017, at which time the Company received 263,012 additional shares based on a final weighted average per share purchase price during the repurchase period of $142.48.

On December 14, 2018, as part of the Program, the Company entered an ASR agreement ("2018 ASR Agreement") with a third-party financial institution to repurchase $220 million of its common stock. Pursuant to the 2018 ASR Agreement, the Company delivered $220 million in cash and received 1,057,035 shares based on a stock price of $176.91 on December 14, 2018. The 2018 ASR Agreement was completed on January 29, 2019, at which time the Company received 117,751 additional shares based on a final weighted average per share purchase price during the repurchase period of $187.27.

The Company accounted for the 2017 and 2018 ASR Agreements as two separate transactions: (i) as shares of reacquired common stock for the shares delivered to the Company upon effectiveness of each ASR agreement and (ii) as a forward contract indexed to the Company's common stock for the undelivered shares. The initial delivery of shares was included in treasury stock at cost and results in an immediate reduction of the outstanding shares used to calculate the weighted average common shares outstanding for basic and diluted earnings per share. The forward contracts indexed to the Company's own common stock met the criteria for equity classification, and these amounts were initially recorded in additional paid-in capital.

Since the beginning of the Program, 9,025,542 shares for an aggregate purchase price of $1.5 billion have been repurchased. There were 4,911,438 common shares totaling $958.7 million, 2,854,959 common shares totaling $402.4 million and 1,259,145 common shares totaling $187.7 million repurchased under the Program during 2018, 2017 and 2016, respectively.