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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 9 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Total compensation expense related to unvested stock-based awards granted to employees, officers and directors | $ 23,738 |
Restricted Stock Units (RSUs) [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Restricted stock units, granted | 260,341 | 388,137
Restricted stock units, weighted average grant date fair value | $ 112.49 | $ 67.58
Stock Appreciation Rights (SARs) [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Restricted stock units, granted | 0 | 0

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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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