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Stock-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Stock-based Compensation Plans (Textual) [Abstract] |  |
Stock-based compensation cost | $ 6,080 | $ 5,642
Cash received from purchase plan purchases | $ 2,100 | $ 2,000
Long Term Incentive Plan |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Shares available for grant under the incentive plan (in shares) | 631,013 |
Restricted Stock Awards |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Awards granted to employees (in shares) | 202,831 |
Weighted average grant fair value of awards granted to employees (in dollars per share) | $ 60.84 |
Restricted Stock Awards | Maximum |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Vesting period (up to) | 5 years |
Employee Stock Purchase Plan |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Shares available for grant under the incentive plan (in shares) | 945,882 |
Shares authorized for issuance (in shares) | 4,500,000 |
Percent of fair market value which employees may purchase common stock | 85.00% |
Shares issued to employee under purchase plan (in shares) | 45,229 | 36,270
Weighted average fair value of employee stock purchase rights issued (in dollars per share) | $ 12.52 | $ 16.22
Performance Award | Long Term Incentive Plan |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Awards granted to employees (in shares) | 30,555 |
Weighted average grant fair value of awards granted to employees (in dollars per share) | $ 67.17 |
Performance period | 2 years |
Vesting period | 3 years |
Percent of granted shares that may be earned (up to) | 200.00% |

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- Definition Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Percent Of Granted Shares That May Be Earned + References No definition available. + Details
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- Definition Weighted average fair value of employee stock purchase rights issued. + References No definition available. + Details
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + 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 (a)(1) -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 The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + 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 (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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