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Equity Based Compensation Plans - Narrative (Details) |  | 1 Months Ended | 12 Months Ended | 24 Months Ended |
--- | --- | --- | --- | --- | ---
Dec. 09, 2014 shares | Dec. 31, 2013 shares | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2017 USD ($) $ / shares shares | Dec. 09, 2015 | Dec. 31, 2011 shares | May 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Number of shares authorized | shares |  |  |  |  |  |  |  | 2,000,000
Accelerated share-based compensation cost |  |  | $ 3,500,000 | $ 0 | $ 0 |  |  |
Intrinsic value of the options outstanding and fully vested |  |  | $ 23,500,000 | $ 12,500,000 |  |  |  |
Average fair value of stock options granted (in dollars per share) | $ / shares |  |  | $ 24.02 | $ 26.13 | $ 22.41 |  |  |
Cap on the appreciation of the market price over the exercise price, option 1 |  |  | $ 100 | $ 100 | $ 100 |  |  |
Cap on the appreciation of the market price over the exercise price, option 2 |  |  | 125 | 125 | 125 |  |  |
Stock Options |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Share based compensation expense |  |  | 11,400,000 | 12,100,000 | 9,800,000 |  |  |
Stock-based compensation capitalized |  |  | 1,600,000 | 2,000,000.0 | 1,500,000 |  |  |
Intrinsic value of options exercised |  |  | 18,700,000 | $ 3,100,000 | $ 16,700,000 |  |  |
Unrecognized compensation cost |  |  | $ 5,300,000 |  |  |  |  |
Unrecognized compensation cost, period for recognition |  |  | 2 years 2 months 12 days |  |  |  |  |
Restricted Stock |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Unrecognized compensation cost |  |  | $ 12,700,000 |  |  |  |  |
Unrecognized compensation cost, period for recognition |  |  | 2 years 1 month 6 days |  |  |  |  |
Granted (in shares) | shares |  |  | 41,643 | 51,945 | 62,706 |  |  |
2015 LTIP Units |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Granted (in shares) | shares | 44,750 |  |  |  |  |  |  |
Units issued subject only to performance measurement | shares | 24,000 |  |  |  |  |  |  |
Vesting percentage of units per year | 20.00% |  |  |  |  |  |  |
Option grants to officers and employees vesting period | 5 years |  |  |  |  |  |  |
Percent of awards earned |  |  |  |  |  | 95.75% |  |
Conversion ratio, incentive units |  |  | 1 |  |  |  |  |
Liquidity measurement period |  |  | 10 years |  |  |  |  |
Measurement period |  |  | 10 years |  |  |  |  |
Series Z Incentive Units |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Granted (in shares) | shares |  | 50,500 |  |  |  |  | 154,500 |
Option grants to officers and employees vesting period |  | 4 years |  |  |  |  |  |
Conversion ratio, incentive units |  |  |  |  |  |  | 1 |
Incentive units conversion ratio |  |  |  |  |  |  | one-for-one |
Series Z Incentive Units | Minimum |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting percentage of units per year |  |  |  |  |  |  | 0.00% |
Option grants to officers and employees vesting period |  |  | 8 years |  |  |  |  |
Series Z Incentive Units | Maximum |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting percentage of units per year |  |  |  |  |  |  | 14.00% |
Option grants to officers and employees vesting period |  |  | 15 years |  |  |  |  |
Long Term Incentive Plan 2014 Units |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting percentage of units per year |  | 25.00% |  |  |  |  |  |
Conversion ratio, incentive units |  |  | 1 |  |  |  |  |
Liquidity measurement period |  |  | 10 years |  |  |  |  |
Measurement period |  |  | 10 years |  |  |  |  |
Vesting percentage for 2011 Z 1 Units to be convertible |  |  |  |  |  |  | 100.00% |
Long Term Incentive Plans - Z Units and 2014 LTIP Units |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |
Share based compensation expense |  |  | $ 900,000 | $ 800,000 | $ 1,500,000 |  |  |
Stock-based compensation capitalized |  |  | 200,000 | $ 200,000 | $ 500,000 |  |  |
Unrecognized compensation cost |  |  | $ 0 |  |  |  |  |
Granted (in shares) | shares |  |  | 0 | 0 | 0 |  |  |
Intrinsic value of vested and unvested LTIP units |  |  | $ 43,700,000 |  |  |  |  |

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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + 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 (a)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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