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Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage

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Share-based Compensation Arrangements By Share-based Payment Award, Award Amortization Period

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Share-based Compensation Arrangements By Share-based Payment Award, Number Of Award Tranches

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Share-based Compensation Arrangements By Share-based Payment Award, Performance Period

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Amount of cost for defined contribution plan.

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Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

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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.

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Amount of cost (reversal of cost) for pension and other postretirement benefits.

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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.

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Additional share-based compensation cost recognized as a result of an occurrence of an event that accelerates its recognition.

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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).

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The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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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.

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Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

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Share-Based Compensation and Other Benefit Plans - Summary of Share-Based Compensation Expense (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2017 tranche	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Dividends \| $		$ 0	$ 0
Share-based compensation (equity-classified) \| $		1,038	1,576
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost \| $			600
Separation Agreement, Consulting Fees \| $				$ 300
Defined Contribution Plan, Cost \| $		200	$ 100
Other Pension, Postretirement and Supplemental Plans [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost) \| $		$ 0
Time Vested Restricted Stock Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares		347,440
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares			$ 36.52
Shares, Issued \| shares		24,657	37,845
Time Vested Restricted Stock Units [Member] \| Minimum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangements By Share-based Payment Award, Award Amortization Period		4 years
Time Vested Restricted Stock Units [Member] \| Maximum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangements By Share-based Payment Award, Award Amortization Period		5 years
Performance Restricted Stock Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares		0	98,526
Share-based Compensation Arrangements By Share-based Payment Award, Award Amortization Period		5 years
Shares, Issued \| shares		1,495	1,495
Share-based Compensation Arrangements By Share-based Payment Award, Performance Period	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum		1.44%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum		1.51%
Performance Restricted Stock Units [Member] \| Minimum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangements By Share-based Payment Award, Number Of Award Tranches \| tranche	2
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage		0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award		0.5963
Performance Restricted Stock Units [Member] \| Maximum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangements By Share-based Payment Award, Number Of Award Tranches \| tranche	3
Share-based Compensation Arrangement by Share-based Payment Award, Shares, Expected to Vest, Percentage		200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award		0.6218
Performance Restricted Stock Units [Member] \| Year 1 [Member] \| Minimum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares		$ 47.70
Performance Restricted Stock Units [Member] \| Year 2 [Member] \| Maximum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares		$ 65.28
Time Vested Restricted Stock Units - Employees [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares		0	5,719
Employees and Directors [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant \| shares		749,600