Share-based incentives	6 Months Ended
Share-based incentives	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based incentives	Share-based incentives. During the first quarters 2016 and 2015, the Company granted executives and senior management shares of restricted common stock which are time-based. Prior to 2016, time-based restricted common stock grants vest at the end of three years after the grant date, while the 2016 grants will vest on each of the first three anniversaries of the grant date. The Company also granted performance-based shares of restricted common stock which vest upon achievement of certain financial objectives over a period of three years. The aggregate fair values of these awards at the grant date in 2016 and 2015 were $3.9 million (105,000 shares with an average grant price of $37.33) and $4.2 million (113,000 shares with an average grant price of $37.04), respectively. Awards were made pursuant to the Company’s employee incentive compensation plans and the compensation expense associated with restricted stock awards is recognized over the corresponding vesting period. Additionally, during the second quarters 2016 and 2015, the Company granted its board of directors, as a component of annual director retainer compensation, 16,300 and 18,200 shares, respectively, of common stock, which immediately vested at the grant date. The aggregate fair values of these director awards at the grant dates in 2016 and 2015 were $0.6 million and 0.7 million, respectively.

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.