Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for annual financial statements. We have omitted certain footnote disclosures that would substantially duplicate the disclosures in our 2016 Annual Report on Form 10-K, unless the information contained in those disclosures materially changed or is required by GAAP. Certain prior year amounts have been reclassified to conform to the current year presentation. In the opinion of management, all adjustments, including normal recurring adjustments, necessary for a fair statement of the consolidated financial statements as of and for the three months ended March 31, 2017 and 2016 have been recorded. The results of operations for the three months ended March 31, 2017 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2017. These unaudited consolidated financial statements should be read in conjunction with our audited consolidated financial statements for the year ended December 31, 2016 included in our 2016 Annual Report on Form 10-K.
Foreign Currency	Certain of our subsidiaries operate outside of the United States and have functional currencies other than the U.S. dollar, or USD. We translate the assets and liabilities of those subsidiaries to USD using the exchange rate in effect at the end of the period. We translate the revenues and expenses of those subsidiaries to USD using the average exchange rates in effect during the period. The net effect of these translation adjustments is included in “Foreign currency translation adjustments” in our consolidated statements of comprehensive income.
Recently Adopted Accounting Guidance	Recently Adopted Accounting Guidance: In March 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, or ASU 2016-09. The amendments in this update simplify several aspects of accounting for and reporting on share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. We adopted the amendments in ASU 2016-09 on January 1, 2017. We prospectively recognized tax benefits of $20.0, or $0.07 per diluted share, for the three months ended March 31, 2017 in the income statement, which previously would have been recorded to additional paid-in capital. In addition, we prospectively recognized excess tax benefits as an operating activity within the cash flow statement for the three months ended March 31, 2017. Finally, we retrospectively recognized taxes paid on the employees' behalf through the withholding of common stock as a financing activity within the cash flow statements for the three months ended March 31, 2017 and 2016.
Recent Accounting Guidance Not Yet Adopted	Recent Accounting Guidance Not Yet Adopted: In March 2017, the FASB issued Accounting Standards Update No. 2017-07, Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, or ASU 2017-07. This amendment requires entities to disaggregate the service cost component from the other components of the benefit cost and present the service cost component in the same income statement line item as other employee compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. In addition, the amendment allows only the service cost component to be eligible for asset capitalization. Upon adoption, the guidance on the presentation of the components of net periodic benefit cost in the income statement is to be applied retrospectively and the guidance limiting the capitalization of net periodic benefit cost in assets to the service cost component is to be applied prospectively. ASU 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted. We are currently evaluating the effects the adoption of ASU 2017-07 will have upon our consolidated financial position, results of operations and cash flows. In January 2017, the FASB issued Accounting Standards Update No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, or ASU 2017-04. This amendment removes Step 2 of the goodwill impairment test under current guidance which requires a hypothetical purchase price allocation. The new guidance requires an impairment charge to be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value. Upon adoption, the guidance is to be applied prospectively. ASU 2017-04 is effective for us on January 1, 2020, with early adoption permitted. The adoption of ASU 2017-04 is not expected to have a material impact on our consolidated financial position, results of operations or cash flows. There were no other new accounting pronouncements that were issued or became effective since the issuance of our 2016 Annual Report on Form 10-K that had, or are expected to have, a material impact on our consolidated financial position, results of operations or cash flows.