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Compensation and Other Benefit Plans - Additional Information (Details) - USD ($) | 1 Months Ended | 12 Months Ended
--- | --- | ---
May. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Deferred savings plan [Abstract] |  |  |  |
Maximum annual contribution per employee (in hundredths) |  | 50.00% |  |
Maximum annual contribution per employee |  | $ 18,000 | $ 17,500 |
Maximum annual contribution per employee over 50 years old |  | $ 24,000 | $ 23,000 |
Age requirement for participant to be eligible for a catch-up contribution, minimum |  | 50 years | 50 years |
Employer matching contribution percentage, maximum (in hundredths) |  | 50.00% |  |
Deferred savings plan expense |  | $ 800,000 | $ 1,000,000 | $ 900,000
Deferred savings plan expense paid in common shares (in hundredths) |  | 100.00% | 100.00% | 100.00%
Number of shares of common stock to be issued upon exercise of options and RSUs outstanding (in shares) |  | 10,148,543 |  |
Directors [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 1 year |  |
Non Executive Employee |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 4 years |  |
Stock Options [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 4 years |  |
Expiration period |  | ten years from the date of the grant or three months from the date of termination of employment (longer in case of death or certain retirements). |  |
Additional disclosures [Abstract] |  |  |  |
Minimum age required for employees to qualify for immediate vesting of RSUs |  | 55 years |  |
Threshold years required for retirement age |  | 70 years |  |
Options exercised, aggregate intrinsic value |  | $ 400,000 | $ 2,900,000 | $ 1,700,000
Options outstanding, aggregate intrinsic value |  | $ 13,000 |  |
Options outstanding, weighted average remaining contractual term |  | 6 years 3 months 18 days |  |
Options exercisable, aggregate intrinsic value |  | $ 10,000 |  |
Options exercisable, weighted average remaining contractual term |  | 5 years 8 months 12 days |  |
Unrecognized compensation expense related to stock options |  | $ 4,800,000 |  |
Weighted average period of unrecognized compensation expense expected to be recognized |  | 2 years 2 months 12 days |  |
Stock options vested and expected to vest [Abstract] |  |  |  |
Options vested and expected to vest, number of shares (in shares) |  | 7,486,402 |  |
Options vested and expected to vest, weighted-average exercise price (in dollars per share) |  | $ 6.37 |  |
Stock option activity [Roll Forward] |  |  |  |
Exercisable at end of year (in shares) |  | 5,604,615 | 4,908,925 | 4,814,926
Stock Options [Member] | Directors [Member] | Minimum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 1 year |  |
Stock Options [Member] | Directors [Member] | Maximum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 3 years |  |
Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 1 year |  |
Additional disclosures [Abstract] |  |  |  |
Minimum age required for employees to qualify for immediate vesting of RSUs |  | 55 years |  |
Threshold years required for retirement age |  | 70 years |  |
Weighted average period of unrecognized compensation expense expected to be recognized |  | 1 year 6 months |  |
Unrecognized compensation expense related to employee RSUs |  | $ 4,900,000 |  |
Unvested RSU activity, weighted average grant date fair value [Roll Forward] |  |  |  |
Total grant-date fair value of RSUs, vested |  | $ 5,500,000 | $ 3,900,000 | $ 1,600,000
Restricted Stock Units (RSUs) [Member] | Directors [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 1 year |  |
Restricted Stock Units (RSUs) [Member] | Employees [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 3 years |  |
2015 ESPP [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Percentage related to employees to purchase shares at the lower fair market value at offering period |  | 85.00% |  |
Common stock reserved for future issuance (in shares) |  | 300,000 |  |
Percentage of compensation of eligible employees to purchase shares of entity common stock at discount through payroll deductions |  | 10.00% |  |
Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Percentage related to employees to purchase shares at the lower fair market value at offering period |  | 95.00% |  |
Shares authorized for issuance (in shares) |  | 233,333 |  |
Employee Stock Purchase Plan [Member] | Maximum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Employee compensation available for share purchases, maximum (in hundredths) |  | 15.00% |  |
1998 and 2015 Employee Stock Purchase Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Shares purchased (in shares) |  | 120,595 | 17,702 | 15,262
Net payroll deductions to acquire shares |  | $ 170,000 | $ 74,000 | $ 60,000
Long Term Incentive Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Expiration period |  | ten years from the date of the grant or three to six months from the date of termination of employment (longer in case of death or certain retirements). |  |
Deferred savings plan [Abstract] |  |  |  |
Shares available for grant |  | 3,935,778 |  |
Long Term Incentive Plan [Member] | Stock Options [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Shares authorized for issuance (in shares) | 18,771,206 |  |  |
Deferred savings plan [Abstract] |  |  |  |
Additional shares authorized for issuance (in shares) | 5,350,000 |  |  |
Reducing shares from number of available shares (in shares) | 1.18 |  |  |

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- Definition 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. + 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)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + 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 (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition 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. + 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)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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