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Stock-based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2019
Stock-based Compensation |
Summary of stock option activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Remaining |  | Aggregate
​ | ​ | ​ | ​ | Exercise | ​ | Contractual Term | ​ | Intrinsic Value
​ |  | Shares |  | Price |  | (in years) |  | (in thousands)(1)
Balance at December 31, 2018 |  | 2,620,295 | ​ | $ | 20.40 |  | 1.49 |  | $ | 25,697
Granted |  | — | ​ | $ | — |  | — | ​ | $ | —
Exercised |  | (1,603,139) | ​ | $ | 20.00 |  | — |  | $ | 29,909
Forfeited/canceled |  | — | ​ | $ | — |  | — |  | $ | —
Balance at September 30, 2019 |  | 1,017,156 | ​ | $ | 21.04 |  | 0.80 |  | $ | 21,138
Vested and exercisable as of September 30, 2019 |  | 1,017,156 | ​ | $ | 21.04 |  | 0.80 |  | $ | 21,138
(1) | The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of our Class A common stock as of the respective date.
Summary of additional information regarding exercisable and vested stock options | ​
​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​
​ | ​ | Stock Options Exercisable
​ | ​ | and Vested
​ |  | ​ |  | Weighted-
​ | ​ | ​ | ​ | Average
​ | ​ | Number of | ​ | Remaining Life
Range of exercise prices | ​ | Shares |  | (in years)
$20.00 |  | 897,156 |  | 0.69
$28.80 |  | 120,000 |  | 1.57
$20.00 - $28.80 |  | 1,017,156 |  | 0.80
Summary of activities for unvested RSUs | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Unvested Restricted Stock Units
​ | ​ | ​ | ​ | Weighted-Average
​ | ​ | Number of | ​ | Grant-Date
​ |  | Shares |  | Fair Value
Unvested at December 31, 2018 |  | 1,055,325 | ​ | $ | 41.66
Granted |  | 670,279 | ​ | $ | 39.64
Vested |  | (271,037) | ​ | $ | 34.58
Forfeited/canceled |  | (202,621) | ​ | $ | 32.40
Unvested at September 30, 2019 |  | 1,251,946 | ​ | $ | 43.62
Expected to vest after September 30, 2019 |  | 1,341,575 | ​ | $ | 43.45

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- Definition Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year. + 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)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of option exercise prices, by grouped ranges, including the upper and lower limits of the price range, the number of shares under option, weighted average exercise price and remaining contractual option terms. + 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=116856206&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + 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 (d) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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