Stock-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Additional Disclosures [Abstract]
Compensation expense, gross	$ 3,848	$ 3,896
Performance-based Shares [Member]
Restricted and Performance Stock Grants [Abstract]
Measuring period for performance-based shares	3 years
Restricted Shares [Member] \| Employees [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures	5.00%
Restricted Shares [Member] \| Executives [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures	0.00%
Restricted Shares [Member] \| Directors [Member]
Restricted and Performance Stock Grants [Abstract]
Estimated forfeitures	0.00%
Restricted Shares [Member] \| Age 60 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage	25.00%
Restricted Shares [Member] \| Age 63 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage	25.00%
Restricted Shares [Member] \| Age 65 [Member]
Restricted and Performance Stock Grants [Abstract]
Vesting percentage	100.00%
Restricted and Performance-Based Shares [Member]
Restricted and performance-based stock, shares [Roll Forward]
Beginning of period (in shares)	870,041
Granted (in shares)	8,000
Vested (in shares)	(36,889)
Forfeited (in shares)	(8,975)
End of period (in shares)	832,177
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward]
Beginning of period (in dollars per share)	$ 34.59
Granted (in dollars per share)	40.11
Vested (in dollars per share)	32.72
Forfeited (in dollars per share)	44.27
End of period (in dollars per share)	$ 34.62
Additional Disclosures [Abstract]
Compensation expense, gross	$ 3,400	3,300
Compensation expense, net of tax	2,500	$ 2,500
Unamortized compensation expense	$ 12,200
Restricted and Performance-Based Shares [Member] \| Employees [Member]
Additional Disclosures [Abstract]
Weighted average period of recognition for unrecognized compensation expense	4 years 1 month 6 days
Restricted and Performance-Based Shares [Member] \| Directors [Member]
Additional Disclosures [Abstract]
Weighted average period of recognition for unrecognized compensation expense	9 months 18 days
Restricted and Performance-Based Shares [Member] \| Executives and Directors [Member]
Restricted and Performance Stock Grants [Abstract]
Expiration of vesting period	3 years
Restricted and Performance-Based Shares [Member] \| Executives and Directors [Member] \| Minimum [Member]
Restricted and Performance Stock Grants [Abstract]
Post vesting holding period for restricted and performance shares issued	1 year
Restricted and Performance-Based Shares [Member] \| Executives and Directors [Member] \| Maximum [Member]
Restricted and Performance Stock Grants [Abstract]
Post vesting holding period for restricted and performance shares issued	2 years

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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