Summary of Significant Accounting Policies - Share Repurchase Program (Details) - USD ($) |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2017 |
Dec. 31, 2016 |
Feb. 28, 2017 |
Apr. 30, 2016 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Open market purchase of treasury shares | $ 3,029,000 | ||||
| Open market purchase of treasury shares, fees | $ 4,000 | $ 21,000 | $ 52,000 | ||
| Treasury Stock | |||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Open market purchase of common shares (in shares) | 108,971 | 529,795 | 1,298,418 | ||
| Open market purchase of treasury shares | $ 760,000 | $ 3,029,000 | $ 6,387,000 | ||
| Common Class A | |||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Stock repurchase program, authorized amount (up to) | $ 15,000,000 | $ 10,000,000 |
| X | ||||||||||
- Definition Payments Of Fees For Repurchase Of Common Stock No definition available.
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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. No definition available.
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- Definition Amount of stock repurchase plan authorized. No definition available.
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- Definition Number of shares that have been repurchased during the period and are being held in treasury. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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