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Stockholders' Equity and Stock Plans - Options Outstanding Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 12 Months Ended
--- | --- | ---
Nov. 21, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Number of Shares |  |  |  |  |
Options outstanding, beginning balance (in shares) |  | 181,789 | 185,269 | 194,672 |
Granted (in shares) |  | 100,664 | 32,637 | 28,320 |
Cancelled, expired or forfeited (in shares) |  | (2,011) |  | (652) |
Exercised (in shares) |  | (21,474) | (36,117) | (37,071) |
Options outstanding, ending balance (in shares) |  | 258,968 | 181,789 | 185,269 | 194,672
Exercisable (vested), ending balance (in shares) |  | 192,172 | 103,211 | 114,581 |
Weighted Average Exercise Price |  |  |  |  |
Options outstanding, beginning balance (usd per share) |  | $ 41.20 | $ 38.35 | $ 35.14 |
Granted (usd per share) |  | 39.78 | 49.37 | 50.70 |
Cancelled, expired or forfeited (usd per share) |  | 43.97 |  | 48.38 |
Exercised (usd per share) |  | 38.62 | 33.98 | 30.72 |
Options outstanding, ending balance (usd per share) |  | 40.84 | 41.20 | 38.35 | $ 35.14
Exercisable (vested), ending balance (usd per share) |  | 35.69 | 36.65 | 34.12 |
Weighted Average Grant-Date Fair Value |  |  |  |  |
Granted (usd per share) |  | $ 32.61 | $ 10.11 | $ 12.21 |
Weighted Average Remaining Contractual Term |  |  |  |  |
Options outstanding |  | 5 years 4 months 2 days | 5 years 9 months 7 days | 5 years | 4 years 5 months 23 days
Exercisable (vested) |  | 4 years 5 months 1 day | 4 years 2 months 4 days | 3 years 2 months 15 days |
Aggregate Intrinsic Value |  |  |  |  |
Options outstanding, beginning balance |  | $ 5,190 | $ 2,788 | $ 3,398 |
Exercised |  | 585 | 661 | 755 |
Options outstanding, ending balance |  | 7,075 | 5,190 | 2,788 | $ 3,398
Exercisable (vested) at year end |  | $ 6,212 | $ 3,416 | $ 2,209 |
Bank of Napa, N.A. (Napa) |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Number of options issued in merger | 70,145 | 70,145 |  |  |
Weighted Average Exercise Price |  |  |  |  |
Options outstanding, ending balance (usd per share) |  | $ 27.20 |  |  |
Weighted Average Grant-Date Fair Value |  |  |  |  |
Granted (usd per share) |  | $ 40.71 |  |  |

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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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