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Equity Compensation Plans - Additional Information (Details) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Oct. 15, 2019 | Dec. 31, 2018 USD ($) $ / shares shares | May 31, 2018 executive $ / shares shares | Dec. 31, 2017 $ / shares | May 31, 2014 | Dec. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2017 $ / shares shares | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2017 USD ($) $ / shares shares | Dec. 31, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares of common stock available for grant under Redwood's Incentive Plan (in shares) |  | 4,616,776 |  |  |  | 4,616,776 |  | 3,637,480 | 4,616,776 |  |
Unrecognized compensation cost | $ |  | $ 25,122 |  |  |  | $ 25,122 |  | $ 32,328 | $ 25,122 |  |
Weighted average amortization period remaining for equity awards (in years) |  |  |  |  |  |  |  | 2 years |  |  |
Equity compensation expense | $ |  |  |  |  |  |  |  | $ 13,402 | $ 12,388 | $ 10,141 |
Share-based compensation, vesting period (in years) | 2 years |  |  |  |  |  |  |  |  |  |
Shares of common stock to be purchased in aggregate for all employees (in shares) |  |  |  |  |  |  |  | 600,000 |  |  |
Number of shares purchased by employees (in shares) |  |  |  |  |  |  |  | 430,772 |  |  |
Number of additional shares authorized |  |  |  |  |  |  |  |  | 200,000 |  |
Restricted Stock Awards |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  |  |  |  |  | $ 2,000 |  |  |
Weighted average amortization period remaining for equity awards (in years) |  |  |  |  |  |  |  | 2 years |  |  |
Equity compensation expense | $ |  |  |  |  |  |  |  | $ 2,000 | $ 2,000 | $ 1,000 |
Number of stock awards granted (in shares) |  |  |  |  |  |  |  | 0 | 168,537 | 134,364 |
Number of stock awards forfeited (in shares) |  |  |  |  |  |  |  | 0 | 7,470 | 19,444 |
Granted (in dollars per share) | $ / shares |  |  |  |  |  |  |  | $ 0 | $ 14.71 | $ 16.52 |
Number of stock awards vested (in shares) |  |  |  |  |  |  |  | 118,136 | 83,968 | 61,928 |
Restricted Stock Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  |  |  |  |  | $ 4,000 |  |  |
Weighted average amortization period remaining for equity awards (in years) |  |  |  |  |  |  |  | 2 years |  |  |
Equity compensation expense | $ |  |  |  |  |  |  |  | $ 1,000 | $ 100 |  |
Number of stock awards granted (in shares) |  |  |  |  |  |  |  | 270,297 | 4,876 | 0 |
Number of stock awards forfeited (in shares) |  |  |  |  |  |  |  | 0 | 0 | 0 |
Granted (in dollars per share) | $ / shares |  |  |  |  |  |  |  | $ 15.66 | $ 15.38 | $ 0 |
Number of stock awards vested (in shares) |  |  |  |  |  |  |  | 0 | 0 | 0 |
Deferred Stock Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  |  |  |  |  | $ 18,000 |  |  |
Equity compensation expense | $ |  |  |  |  |  |  |  | $ 8,000 | $ 8,000 | $ 6,000 |
Unvested outstanding stock awards (in units) |  | 1,155,098 |  |  |  | 1,155,098 |  | 1,344,743 | 1,155,098 |  |
Weighted-average grant date fair value of stock awards (in dollars per unit) | $ / shares |  | $ 15.18 |  |  |  | $ 15.18 |  | $ 15.76 | $ 15.18 |  |
Number of stock awards vested (in units) |  | 1,181,623 |  |  |  | 1,181,623 |  | 1,286,063 | 1,181,623 |  |
Number of stock awards granted (in shares) |  |  |  |  |  |  |  | 733,096 | 670,254 | 565,921 |
Number of stock awards forfeited (in shares) |  |  |  |  |  |  |  | 19,898 | 0 | 31,875 |
Granted (in dollars per share) | $ / shares |  |  |  |  |  |  |  | $ 16.06 | $ 15.53 | $ 16.01 |
Performance Stock Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  |  |  |  |  |  | $ 9,000 |  |  |
Equity compensation expense | $ |  |  |  |  |  |  |  | $ 3,000 | $ 3,000 | $ 3,000 |
Unvested outstanding stock awards (in units) |  | 725,616 |  |  |  | 725,616 |  | 839,070 | 725,616 |  |
Weighted-average grant date fair value of stock awards (in dollars per unit) | $ / shares |  | $ 17.05 |  | $ 13.24 |  | $ 17.05 | $ 13.24 | $ 17.13 | $ 17.05 | $ 13.24 |
Number of stock awards granted (in shares) |  |  |  |  |  |  |  | 307,938 | 258,078 | 273,054 |
Number of stock awards forfeited (in shares) |  |  |  |  |  |  |  | 0 | 0 | 0 |
Share-based compensation, vesting period (in years) |  |  |  |  |  |  |  | 3 years |  |  | 3 years
TSR performance period (in years) |  |  |  |  |  |  |  | 3 years |  |  |
Grant date fair value assumptions, dividend rate, risk-free rate, treasury rate measurement period (in years) |  |  |  |  |  |  |  | 3 years |  |  |
Performance Stock Units | Executives |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of stock awards granted (in shares) |  |  | 23,025 |  |  |  |  |  |  |  |
Stock price valuation period |  |  | 60 days |  |  |  |  |  |  |  |
Grant date fair value assumptions, volatility rate |  |  | 27.00% |  |  |  |  |  |  |  |
Grant date fair value assumptions, risk-free rate |  |  | 2.71% |  |  |  |  |  |  |  |
Grant date fair value assumptions, dividend yield |  |  | 0.00% |  |  |  |  |  |  |  |
Granted (in dollars per share) | $ / shares |  |  | $ 15.20 |  |  |  |  |  |  |  |
Number of executives granted PSUs in connection with promotions | executive |  |  | 2 |  |  |  |  |  |  |  |
Performance Stock Units | Performance Share Units (PSUs), 2018 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of stock awards granted (in shares) |  |  |  |  |  |  |  | 307,938 | 235,053 |  |
Share-based compensation, vesting period (in years) |  |  |  |  |  |  |  | 3 years |  |  |
Vesting percentage if bvTSR is 25% |  | 100.00% |  |  |  |  |  |  |  |  |
Relative increase/decrease in vesting percentage based on rTSR |  | 50.00% |  |  |  |  |  |  |  |  |
Vesting percentage cap if first 2 steps yield a vesting level greater than 100% |  | 100.00% |  |  |  |  |  |  |  |  |
Stock price valuation period |  | 60 days |  |  |  |  |  |  |  |  |
Grant date fair value (in dollars per share) | $ / shares |  | $ 17.23 |  |  |  |  |  | $ 17.13 |  |  |
Grant date fair value assumptions, volatility rate |  | 22.00% |  |  |  |  |  | 15.00% |  |  |
Grant date fair value assumptions, risk-free rate |  | 2.78% |  |  |  |  |  | 1.68% |  |  |
Grant date fair value assumptions, dividend yield |  | 0.00% |  |  |  |  |  | 0.00% |  |  |
Performance Stock Units | Performance Share Units (PSUs), 2017 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share-based compensation, vesting period (in years) |  |  |  |  |  |  |  |  |  | 3 years |
Stock price valuation period |  |  |  |  |  |  |  |  |  | 60 days |
Grant date fair value assumptions, volatility rate |  |  |  |  |  |  |  |  |  | 27.00% |
Grant date fair value assumptions, risk-free rate |  |  |  |  |  |  |  |  |  | 1.90% |
Grant date fair value assumptions, dividend yield |  |  |  |  |  |  |  |  |  | 0.00% |
TSR performance period (in years) |  |  |  |  |  |  |  |  |  | 3 years |
Award vesting rights, total share return, percentage |  |  |  | 125.00% |  |  |  |  |  |  |
Performance Stock Units | Performance Share Units (PSUs), 2016 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
TSR performance period (in years) |  |  |  |  |  |  |  |  |  |  | 2 years
Grant date fair value assumptions, average closing stock price of common stock, measurement period (in days) |  |  |  |  |  |  |  |  |  |  | 60 days
Number of stock awards vested (in shares) |  |  |  |  |  |  |  |  |  |  | 222,769
Performance Stock Units | Performance Share Units (PSUs), 2015 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of stock awards vested (in shares) |  |  |  |  |  | 387,937 | 0 |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share-based compensation, vesting period (in years) |  |  |  |  | 4 years |  |  |  |  |  |
Maximum | Deferred Stock Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Weighted average amortization period remaining for equity awards (in years) |  |  |  |  |  |  |  | 2 years |  |  |
Maximum | Performance Stock Units | Performance Share Units (PSUs), 2018 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Vesting percentage |  | 250.00% |  |  |  |  |  |  |  |  |
First baseline vesting percentage |  | 200.00% |  |  |  |  |  |  |  |  |
Maximum | Performance Stock Units | Performance Share Units (PSUs), 2017 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Equity awards, vesting percentage |  |  |  | 200.00% |  |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share-based compensation, vesting period (in years) |  |  |  |  | 3 years |  |  |  |  |  |
Minimum | Performance Stock Units | Performance Share Units (PSUs), 2018 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Vesting percentage |  | 0.00% |  |  |  |  |  |  |  |  |
First baseline vesting percentage |  | 0.00% |  |  |  |  |  |  |  |  |
Minimum | Performance Stock Units | Performance Share Units (PSUs), 2017 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Equity awards, vesting percentage |  |  |  | 0.00% |  |  |  |  |  |  |

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition 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. + 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 (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + 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 (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + 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 (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Number of additional shares authorized for issuance under share-based payment arrangement. + References No definition available. + 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://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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