Share-Based Compensation - RSU Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Grant Date Fair Value
Share-based compensation	$ 20,962	$ 15,660	$ 14,395
Earned Restricted Stock Units
Number of Shares
Non-vested RSUs, beginning balance (in shares)	911,165	1,006,009	971,751
Granted (in shares)	268,360	723,045	723,654
Vested (in shares)	(397,451)	(657,814)	(532,815)
Forfeited (in shares)	(39,722)	(160,075)	(156,581)
Non-vested RSUs, ending balance (in shares)	742,352	911,165	1,006,009
Weighted Average Grant Date Fair Value
Non-vested RSUs, beginning balance (in dollars per share)	$ 28.74	$ 37.88	$ 37.08
Granted (in dollars per share)	32.29	26.96	37.80
Vested (in dollars per share)	29.60	38.67	36.57
Forfeited (in dollars per share)	31.13	37.34	37.01
Non-vested RSUs, ending balance (in dollars per share)	$ 29.44	$ 28.74	37.88
Performance Restricted Stock Units
Number of Shares
Granted (in shares)	118,367	304,114
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 33.75	$ 22.84
Market Based Restricted Stock Units
Number of Shares
Granted (in shares)	118,285	134,989
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 49.21	$ 24.13
Restricted Stock Units
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 32.29	$ 26.96	$ 37.80
Total fair value of restricted stock vested	$ 12,700	$ 16,700	$ 26,000
Share-based compensation	19,500	$ 15,100	$ 14,500
Unrecognized compensation expense	$ 9,300
Weighted-average period for recognition of compensation cost	1 year 8 months 12 days

Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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).

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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 number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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