Stock Based Compensation	3 Months Ended
Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	STOCK-BASED COMPENSATION The Company’s 2017 Stock Incentive Plan, or the 2017 Plan, permits stock-based compensation awards to officers, directors, employees, and consultants. As of March 31, 2018, the 2017 Plan authorized grants of stock‑based compensation instruments to purchase or issue up to 4,000,000 shares of Company common stock. As of March 31, 2018, there were 3,537,972 shares available for grant under the 2017 Plan. Though frozen for new issuances, certain awards issued under the 2003 Stock Incentive Plan, or the 2003 Plan, remain outstanding. Restricted Stock Restricted stock amortization totaled $7.2 million, $5.4 million, and $6.5 million for the three months ended March 31, 2018, December 31, 2017 and March 31, 2017. Such amounts are included in "Compensation expense" on the condensed consolidated statements of earnings. The amount of unrecognized compensation expense related to unvested TRSAs and PRSUs as of March 31, 2018 totaled $52.1 million. Time-Based Restricted Stock Awards At March 31, 2018, there were 1,383,914 shares of unvested TRSAs outstanding pursuant to the Company's 2003 and 2017 Stock Incentive Plans (the "Plans"). The TRSAs generally vest ratably over a service period of three or four years from the date of the grant or immediately upon death of an employee. Compensation expense related to TRSAs is based on the fair value of the underlying stock on the award date and is recognized over the vesting period using the straight‑line method. Performance-Based Restricted Stock Units At March 31, 2018, there were 325,741 unvested PRSUs granted. The PRSUs will vest only if performance goals with respect to certain financial metrics are met over a three-year performance period. The PRSUs are not considered issued and outstanding under either the 2017 Plan or the 2003 Plan until they vest. PRSUs are granted and initially expensed based on a target number. The number of shares that will ultimately vest based on actual performance will range from zero to a maximum of either 150% or 200% of target. Compensation expense related to PRSUs is based on the fair value of the underlying stock on the award date and is amortized over the vesting period using the straight-line method unless it is determined that: (1) attainment of the financial metrics is less than probable, in which case a portion of the amortization is suspended, or (2) attainment of the financial metrics is improbable, in which case a portion of the previously recognized amortization is reversed and also suspended. If it is determined that attainment of a financial measure higher than target is probable, the amortization will increase to up to 150% or 200% of the target amortization amount. Annual PRSU expense may vary during the three-year performance period based upon changes in management's estimate of the number of shares that may ultimately vest. In the case where the performance target for the PRSU is based on a market condition (such as total shareholder return), the amortization is neither reversed nor suspended if it is subsequently determined that the attainment of the performance target is less than probable or improbable.

STOCK-BASED COMPENSATION

The Company’s 2017 Stock Incentive Plan, or the 2017 Plan, permits stock-based compensation awards to officers, directors, employees, and consultants. As of March 31, 2018, the 2017 Plan authorized grants of stock‑based compensation instruments to purchase or issue up to 4,000,000 shares of Company common stock. As of March 31, 2018, there were 3,537,972 shares available for grant under the 2017 Plan. Though frozen for new issuances, certain awards issued under the 2003 Stock Incentive Plan, or the 2003 Plan, remain outstanding.

Restricted Stock

Restricted stock amortization totaled $7.2 million, $5.4 million, and $6.5 million for the three months ended March 31, 2018, December 31, 2017 and March 31, 2017. Such amounts are included in "Compensation expense" on the condensed consolidated statements of earnings. The amount of unrecognized compensation expense related to unvested TRSAs and PRSUs as of March 31, 2018 totaled $52.1 million.

Time-Based Restricted Stock Awards

At March 31, 2018, there were 1,383,914 shares of unvested TRSAs outstanding pursuant to the Company's 2003 and 2017 Stock Incentive Plans (the "Plans"). The TRSAs generally vest ratably over a service period of three or four years from the date of the grant or immediately upon death of an employee. Compensation expense related to TRSAs is based on the fair value of the underlying stock on the award date and is recognized over the vesting period using the straight‑line method.

Performance-Based Restricted Stock Units

At March 31, 2018, there were 325,741 unvested PRSUs granted. The PRSUs will vest only if performance goals with respect to certain financial metrics are met over a three-year performance period. The PRSUs are not considered issued and outstanding under either the 2017 Plan or the 2003 Plan until they vest. PRSUs are granted and initially expensed based on a target number. The number of shares that will ultimately vest based on actual performance will range from zero to a maximum of either 150% or 200% of target. Compensation expense related to PRSUs is based on the fair value of the underlying stock on the award date and is amortized over the vesting period using the straight-line method unless it is determined that: (1) attainment of the financial metrics is less than probable, in which case a portion of the amortization is suspended, or (2) attainment of the financial metrics is improbable, in which case a portion of the previously recognized amortization is reversed and also suspended. If it is determined that attainment of a financial measure higher than target is probable, the amortization will increase to up to 150% or 200% of the target amortization amount. Annual PRSU expense may vary during the three-year performance period based upon changes in management's estimate of the number of shares that may ultimately vest. In the case where the performance target for the PRSU is based on a market condition (such as total shareholder return), the amortization is neither reversed nor suspended if it is subsequently determined that the attainment of the performance target is less than probable or improbable.