Employee Benefit Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Outstanding stock options and warrants	552,373	599,902
Possible future share issuance authorized under equity incentive plans	1,926,324	2,016,659
Total shares reserved for future issuance	2,478,697	2,616,561
Possible future share issuance authorized under equity incentive plan restricted stock	300,000
Stock-based compensation expense	$ 6,210	$ 7,180	$ 7,466
Total unrecognized stock-based compensation costs	$ 5,200
Weighted average remaining term of vesting periods (in years)	1 year 10 months 24 days
401(k) Savings Plan [Abstract]
401(k) employer match percentage	75.00%
401(k) employer match salary limit percentage	6.00%
401(k) employer contribution	$ 1,400	1,500	1,400
Retirement Plan [Abstract]
Retirement plan qualification years of service (in years)	30 years
Retirement plan qualification age	55 years
Retirement plan qualification minimum years of service (in years)	10 years
Retirement plan immediate vesting percentage	100.00%
Deferred Compensation [Abstract]
Marketable securities of non-qualified deferred compensation plan fair value disclosure	$ 2,573	2,345
Non Qualified Deferred Compensation Obligation Fair Value Disclosure [Roll Forward]
Beginning deferred compensation liability	2,345	1,849	2,388
Mark to market adjustment to deferred compensation (in general and administrative expenses)	228	496	(182)
Distributions from deferred compensation plans	0	0	(357)
Ending deferred compensation liability	$ 2,573	$ 2,345	$ 1,849
Employee Stock Purchase Plan [Abstract]
Employee stock purchase plan salary limit percentage	25.00%
Employee stock purchase plan market percentage	85.00%
Number of days at end of quarter used to calculate ESPP discount	5 days
Shares of Common Stock issued under the employee stock purchase plans	47,208	38,618	38,951
Discount percentage on newly issues shares	15.00%
Discount on newly issued shares expensed as additional compensation	$ 300	$ 300	$ 300
Minimum [Member]
Retirement Benefits [Abstract]
Officer cash bonus target	35.00%
Officer cash bonus performance factor	0.00%
Non officer management cash bonus target	10.00%
Maximum [Member]
Retirement Benefits [Abstract]
Officer cash bonus target	130.00%
Officer cash bonus performance factor	200.00%
Non officer management cash bonus target	30.00%
2017 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Forfeited (in shares)	(46,852)
2016 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Forfeited (in shares)		(9,521)
2015 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Forfeited (in shares)			(13,707)
Stock Options [Member]
Stock Option Activity Rollforward [Abstract]
Balance of options outstanding (in shares)	584,902	596,518	640,822
Options exercised (in shares)	(42,163)	(9,026)	(44,304)
Options forfeited (in shares)	(5,366)	(2,590)
Balance of options outstanding (in shares)	537,373	584,902	596,518
Stock Option Activity, Weighted Average Exercise Price Rollforward [Abstract]
Options outstanding, weighted average exercise price (in dollars per share)	$ 45.75	$ 45.67	$ 45.29
Options exercised, weighted average exercise price (in dollars per share)	41.10	39.53	40.15
Options forfeited, weighted average exercise price (in dollars per share)	50.82	48.79
Options outstanding, weighted average exercise price (in dollars per share)	$ 46.07	$ 45.75	$ 45.67
Weighted average remaining life of outstanding options (in years)	5 years
Options exercisable (in shares)	496,656
Weighted average exercise price (in dollars per share)	$ 45.54
Weighted average remaining life (in years)	4 years 10 months 24 days
Intrinsic value	$ 100
Amount of exercisable options with prices higher than the market price of Company Common Stock	436,880
Cash received or receivable from options exercised	$ 1,900	$ 400	$ 1,900
Total instrinsic value of options exercised	400	100	400
Total intrinsic value of options outstanding	$ 100	$ 2,400	$ 100
2014 to 2017 Stock Options [Member]
Retirement Benefits [Abstract]
Vesting term of stock options issued/Period for absolute total return of restricted stock issued (in years)	4 years
Option expiration period (in years)	10 years
Time-Based Restricted Stock [Member]
Retirement Benefits [Abstract]
Vesting term of stock options issued/Period for absolute total return of restricted stock issued (in years)	4 years
Restricted Stock Activity Rollforward [Abstract]
Balance of restricted stock outstanding (in shares)	218,151	191,239	172,246
Awarded and issued (in shares)	83,116	103,590	94,984
Vested (in shares)	(88,326)	(73,036)	(73,307)
Forfeited (in shares)	(3,751)	(3,642)	(2,684)
Balance of restricted stock outstanding (in shares)	209,190	218,151	191,239
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value (in dollars per share)	$ 45.73	$ 45.62	$ 46.46
Awarded and issued, weighted average grant date fair value (in dollars per share)	44.88	45.98	43.01
Vested, weighted average grant date fair value (in dollars per share)	45.86	45.79	44.19
Forfeited, weighted average grant date fair value (in dollars per share)	45.78	46.07	45.89
Restricted stock outstanding, weighted average grant date fair value (in dollars per share)	45.34	45.73	45.62
Grant date fair value of restricted stock (in dollars per share)	$ 44.88	$ 45.98	$ 43.01
Fair value at grant date of restricted stock issued	$ 3,700	$ 4,800	$ 4,100
Vesting date fair value of restricted stock	$ 3,900	$ 3,300	$ 3,200
Total Return-Based Restricted Stock [Member]
Retirement Benefits [Abstract]
Vesting term of stock options issued/Period for absolute total return of restricted stock issued (in years)	3 years
Assumptions Used in Determining Fair Values of Restricted Stock Granted:
Risk free interest rate	0.90%	2.40%	2.30%
Common stock dividend yield	3.90%	4.40%	3.90%
Expected volatility rate	20.40%	27.30%	41.10%
Dividends paid for previous year	1 year
Restricted Stock Activity Rollforward [Abstract]
Balance of restricted stock outstanding (in shares)	208,848	180,094	160,724
Awarded and issued (in shares)	66,188	87,344	77,456
Vested (in shares)		(45,901)	(41,160)
Forfeited (in shares)	(49,852)	(12,689)	(16,926)
Balance of restricted stock outstanding (in shares)	225,184	208,848	180,094
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value (in dollars per share)	$ 42.22	$ 43.34	$ 44.72
Awarded and issued, weighted average grant date fair value (in dollars per share)	38.31	39.42	40.81
Vested, weighted average grant date fair value (in dollars per share)		43.68	45.61
Forfeited, weighted average grant date fair value (in dollars per share)	51.93	43.58	45.24
Restricted stock outstanding, weighted average grant date fair value (in dollars per share)	$ 39.53	$ 42.22	43.34
Company total return, total return-based restricted stock	100.00%
Vesting percentage, total return-based restricted stock	100.00%	75.00%
Grant date fair value of restricted stock (in dollars per share)	$ 38.31	$ 39.42	$ 40.81
Fair value at grant date of restricted stock issued	$ 2,500	$ 3,400	$ 3,200
Vesting date fair value of restricted stock	$ 0	$ 2,100	$ 1,800
Period preceding date of grant	3 months
Total Return-Based Restricted Stock [Member] | Minimum [Member]
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Percentage of return-based restricted stock issued to officers that will vest	0.00%
Total Return-Based Restricted Stock [Member] | Maximum [Member]
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Percentage of return-based restricted stock issued to officers that will vest	150.00%
Total Return-Based Restricted Stock Current Year Issuance [Member]
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Awarded and issued, weighted average grant date fair value (in dollars per share)	$ 38.31	$ 39.42	$ 40.81
Grant date fair value of restricted stock (in dollars per share)	$ 38.31	$ 39.42	$ 40.81