Share-Based Compensation Arrangements	6 Months Ended
Share-Based Compensation Arrangements	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Arrangements	Share-Based Compensation Arrangements During the six months ended June 30, 2017, the Corporation granted equity awards, which included performance share awards and nonvested share unit awards. The performance share awards granted to certain executive officers provides them with the opportunity to earn shares of common stock of the Corporation. The performance share awards were valued at fair market value as of January 19, 2017 (the award date), or $51.85, and will be earned over a 3-year performance period. The number of shares earned will range from zero to 200% of the target number of shares dependent upon the Corporation’s core return on equity and core earnings per share growth ranking compared to an industry peer group. The current assumption based on the most recent peer group information available results in shares earned at 143% of the target, or 37,147 shares. The Corporation granted to non-employee directors and a certain executive officer 7,900 nonvested share units, with 3- to 5-year cliff vesting. The weighted average grant date fair value of the nonvested share units was $50.83.

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.