Organization, Consolidation and Presentation of Financial Statements (Policies)	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Consolidation	Basis of Consolidation—The unaudited condensed consolidated financial statements include the accounts of West and its wholly-owned subsidiaries. The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto, together with Management’s Discussion and Analysis of Financial Condition and Results of Operations, contained in our Annual Report on Form 10-K for the year ended December 31, 2016. All intercompany balances and transactions have been eliminated in the consolidated financial statements. Our results for the three and six months ended June 30, 2017 are not necessarily indicative of what our results will be for other interim periods or for the full fiscal year.
Use of Estimates	Use of Estimates—The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition—Revenue is recognized when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, price is fixed or determinable and collectability is reasonably assured. Amounts billed in advance of providing service are deferred and recorded as deferred revenue or other long-term liabilities on the balance sheet until service has been provided.
Income Tax	Income Tax—For the three and six months ended June 30, 2017, income tax expense was $22.7 million and $44.2 million, respectively, and the effective income tax rate was 33.6% and 30.9%, respectively. For the three and six months ended June 30, 2016, income tax expense was $18.4 million and $43.2 million, respectively, and the effective income tax rate was 35.8% for both periods. The reduction in the effective tax rate was due primarily to several tax settlements. These settlements decreased our liability for uncertain tax positions by $15.7 million during the first quarter of 2017.
Dividend	Dividend—On May 9, 2017, we announced the payment of future dividends had been suspended. The declaration and payment of all future dividends, if any, will be at the sole discretion of our Board of Directors. We funded the dividends paid in 2016 and the first three months of 2017 with cash generated by our operations. On March 2, 2017, we paid a $0.225 per common share quarterly dividend. The total dividend paid was approximately $18.8 million to stockholders of record as of the close of business on February 21, 2017.
Share Repurchase	Share Repurchase—Under a share repurchase program approved by the Company’s Board of Directors during the first quarter of 2016 authorizing the repurchase of up to an aggregate of $75 million of outstanding common stock, the Company purchased 1,000,000 shares of common stock through the open market during the first quarter of 2016 for an aggregate purchase price of approximately $22.0 million, which was funded with cash on hand. There were no shares repurchased during the second quarter of 2016 or the first and second quarters of 2017.
Assets Held for Sale	Assets Held for Sale—On June 21, 2016, we completed the sale of land, buildings and improvements which were previously classified as held for sale. Proceeds from the sale were $38.8 million, excluding related expenses. In connection with this sale, we realized a pre-tax gain of approximately $19.0 million. We also entered into a 12-year leaseback agreement for one of the buildings. This lease is classified as an operating lease and the related $6.1 million gain, included in the $19.0 million realized gain is being deferred and recognized over the lease term.
Recently Implemented Accounting Pronouncements	Recently Implemented Accounting Pronouncements—In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2016-09, Compensation-Stock Compensation (Topic 718). The new guidance requires excess tax benefits and tax deficiencies to be recorded in the income statement when the awards vest or are settled. In addition, cash flows related to excess tax benefits are no longer separately classified as a financing activity apart from other income tax cash flows. The standard also allows us to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting, clarifies that all cash payments made on an employee’s behalf for withheld shares should be presented as a financing activity on our consolidated cash flows statement, and provides an accounting policy election to account for forfeitures as they occur. Under the new guidance, we elected to change our forfeiture policy to recognize forfeitures of awards as they occur beginning January 1, 2017. The change in forfeiture policy was adopted using a modified-retrospective transition method. We recorded a cumulative-effect adjustment which increased our retained deficit by $0.1 million upon transition on January 1, 2017. We elected to apply the presentation requirements for cash flows related to excess tax benefits prospectively. For the six months ended June 30, 2016, excess tax benefits on stock options recognized in additional paid-in capital was $0.3 million. This is included in the “Proceeds from stock options and Employee Stock Purchase Plan (“ESPP”) shares” line in the condensed consolidated statement of cash flows. The impact of this standard on our consolidated financial statements at the time of implementation was not material, however, the impact on our provision for income taxes in future periods will be dependent on the market price of our common stock on vesting dates of restricted stock awards compared to the fair value of those awards when they were granted.
Recent Accounting Pronouncements	Recent Accounting Pronouncements—In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350). This update addresses the subsequent measurement of goodwill and eliminates Step 2 from the goodwill impairment test. Under the amendments in this update, annual or interim goodwill impairment tests are to be performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, the income tax effects should be considered for any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss. The amendment also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. Therefore, the same impairment assessment applies to all reporting units. The amendment requires disclosure of the amount of goodwill allocated to each reporting unit with a zero or negative carrying amount of net assets. The amendments in this update should be applied on a prospective basis. This amendment will be effective for us in January 2020. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is in the process of assessing the impact of this standard on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows – Restricted Cash (Topic 230). The standard requires entities to include in their cash and cash-equivalent balances in the statement of cash flows those amounts that are deemed to be restricted cash and restricted cash equivalents. The ASU does not define the terms “restricted cash” and “restricted cash equivalents.” The amendment is effective for public business entities for fiscal years beginning after December 15, 2017 and interim periods within those fiscal years and is to be applied using a retrospective transition method to each period presented. Early adoption is permitted. Based on our preliminary assessment, we do not believe there will be a material impact to our consolidated statement of cash flows upon adoption. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows – Classification of Certain Cash Receipts and Cash Payments (Topic 230). The amendments in this update address eight specific cash flow issues with the objective of reducing the existing diversity in practice. This amendment is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the amendments in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. An entity that elects early adoption must adopt all of the amendments in the same period. The amendments in this update should be applied using a retrospective transition method to each period presented. If it is impracticable to apply the amendments retrospectively for some of the issues, the amendments for those issues would be applied prospectively as of the earliest date practicable. Based on our preliminary assessment, we do not believe there will be a material impact to our consolidated statement of cash flows upon adoption. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326). The amendments in this update will require a financial asset (or a group of financial assets) measured on an amortized cost basis to be presented at the net amount expected to be collected. This amendment is effective for public business entities for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018. Adoption of this update is required through a cumulative-effect adjustment to retained deficit as of the beginning of the first reporting period in which the guidance is effective (that is, a modified-retrospective approach). The Company is in the process of assessing the impact of this standard on its financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The amendments in this update will increase the transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. This amendment is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. ASU 2016-02 is required to be applied with a modified retrospective approach to each prior reporting period presented. The Company is in the process of assessing the impact of this standard on its financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). This standard requires the recognition of revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which a Company expects to be entitled in exchange for those goods or services. The new standard also requires enhanced disclosures about the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. We plan to adopt ASU 2014-09 on January 1, 2018. The new standard can be adopted either retrospectively to each prior reporting period presented or as a cumulative-effect adjustment as of the date of adoption. We will likely adopt this accounting standard on a cumulative-effect method, which would result in an adjustment to retained earnings for the cumulative effect, if any, of applying the standard to contracts in process as of the adoption date. Based on our preliminary assessment, we do not believe there will be a material impact to our revenues upon adoption. We are continuing to evaluate the impacts of our pending adoption of this standard and our preliminary assessments are subject to change. Our implementation efforts are progressing as planned.