Stock-based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted-average exercise price per share:
Compensation expense recorded during the year	$ 24,771	$ 25,251	$ 20,697
Stock Options
Stock-Based Compensation
Percentage of the award vesting at each of the three anniversaries	33.00%
Contractual term of the stock options	10 years
Fair Value Assumptions
Expected volatility (as a percent)	30.00%	30.00%	31.00%
Expected dividends (as a percent)	0.00%	0.00%	0.00%
Risk-free rate, Minimum (as a percent)	2.50%	1.70%	0.80%
Risk-free rate, Maximum (as a percent)	2.70%	3.00%	2.70%
Summary of equity awards, options
Balance at beginning of year (in units)	3,693	3,457	2,738
Granted (in units)	344	674	861
Exercised (in units)	(317)	(322)	(90)
Forfeited or canceled (in units)	(21)	(116)	(52)
Balance at end of year (in units)	3,699	3,693	3,457
Weighted-average exercise price per share:
Outstanding at beginning of year (in dollars per share)	$ 17.81	$ 16.40	$ 15.81
Granted (in dollars per share)	22.92	24.40	18.05
Exercised (in dollars per share)	16.26	16.24	15.04
Forfeited	20.70	18.46	15.58
Outstanding at end of year (in dollars per share)	$ 18.40	$ 17.81	$ 16.40
Compensation expense recorded during the year	$ 3,292	$ 6,218	$ 4,909
Number of options exercisable at end of year	2,676
Weighted average exercise price per exercisable option	$ 16.91
Weighted-average remaining contractual term:
Outstanding at end of year	6 years 3 months 18 days
Exercisable at end of year	5 years 6 months
Aggregate intrinsic value
Outstanding at end of year	$ 57,858
Exercisable at end of year	$ 45,837
Number of shares expected to vest	929
Weighted-average vesting period (in months)	9 months
Minimum \| Stock Options
Fair Value Assumptions
Expected grantee forfeiture rate (as a percent)	2.30%	0.00%	0.00%
Maximum \| Stock Options
Fair Value Assumptions
Expected grantee forfeiture rate (as a percent)	22.70%	23.20%	21.10%

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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 number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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