Stock-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Additional Disclosures [Abstract]
Compensation expense, gross	$ 5,742	$ 5,614
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)	204,650
Vested (in shares)	(68,945)
Forfeited (in shares)	(11,950)
End of period (in shares)	993,796
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)	42.05
Vested (in dollars per share)	28.89
Forfeited (in dollars per share)	44.11
End of period (in dollars per share)	$ 36.40
Additional Disclosures [Abstract]
Compensation expense, gross	$ 5,300	5,000
Compensation expense, net of tax	3,900	$ 3,700
Unamortized compensation expense	$ 17,900
Restricted and Performance-Based Shares [Member] \| Employees [Member]
Additional Disclosures [Abstract]
Weighted average period of recognition for unrecognized compensation expense	3 years 10 months 24 days
Restricted and Performance-Based Shares [Member] \| Directors [Member]
Additional Disclosures [Abstract]
Weighted average period of recognition for unrecognized compensation expense	7 months 6 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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