Employee Benefit Plans (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Officer cash bonus target minimum		35.00%
Officer cash bonus target maximum		130.00%
Officer cash bonus performance factor minimum		0.00%
Officer cash bonus performance factor maximum		200.00%
Other management cash bonus target minimum		6.00%
Other management cash bonus target maximum		30.00%
Outstanding stock options and warrants		602,115		702,228
Possible future share issuance authorized under equity incentive plans		2,718,296		3,084,158
Total shares reserved for future issuance		3,320,411		3,786,386
Possible future share issuance authorized under equity incentive plan restricted stock		1,000,000
Stock-based compensation expense		$ 6,251		$ 6,884		$ 6,939
Total unrecognized stock-based compensation costs		$ 5,100
Weighted average remaining term of vesting periods (in years)		2 years 2 months 12 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		$ 1,300		1,300		1,200
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		$ 2,451		2,736		3,635
Non Qualified Deferred Compensation Obligation Fair Value Disclosure [Roll Forward]
Beginning deferred compensation liability		2,736		3,635		3,996
Mark to market adjustment to deferred compensation (in general and administrative expenses)		222		(32)		235
Distributions from deferred compensation plans		(507)		(867)		(596)
Ending deferred compensation liability		$ 2,451		$ 2,736		$ 3,635
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		27,773		29,496		28,682
Employee Stock Purchase Plan Market Percentage Discount		15.00%
Discount on newly issued shares expensed as additional compensation		$ 200		$ 200		$ 200
2012 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Awarded and issued	[1]			61,860
Vested	[1]			(61,860)
2013 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Awarded and issued	[1]	6,647
Vested	[1]	(6,647)
Stock Options [Member]
Stock Option Activity Rollforward [Abstract]
Balance of options outstanding		687,228	[2],[3]	577,321		874,382
Options granted		244,664		197,408		190,330
Options canceled		(14,743)		(3,829)		(134,628)
Options exercised		(330,034)		(83,672)		(352,763)
Balance of options outstanding		587,115	[2],[3]	687,228	[2],[3]	577,321
Stock Option Activity, Weighted Average Exercise Price Rollforward [Abstract]
Options outstanding, weighted average exercise price		$ 37.97		$ 34.92		$ 32.24
Options granted, weighted average exercise price		43.55		45.61		37.90
Options canceled, weighted average exercise price		42.64		40.21		41.93
Options exercised, weighted average exercise price		34.26		34.89		27.21
Options outstanding, weighted average exercise price		$ 42.26	[2],[3]	$ 37.97		$ 34.92
Weighted average remaining life of outstanding options		7 years 10 months 24 days
Options exercisable		74,080
Weighted average exercise price		$ 40.28
Weighted average remaining life		6 years 7 months 6 days
Intrinsic value		$ 800
Cash received or receivable from options exercised		13,400		$ 3,300		$ 11,100
Total instrinsic value of options exercised		4,800		900		5,000
Total intrinsic value of options outstanding		$ 5,100		$ 4,300		$ 5,400
Prior to 2005 and after 2013 Stock Options [Member]
Compensation and Retirement Disclosure [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
Grant date fair value of each stock option granted (in dollars per option)		$ 4.61
Assumptions Used in Determining Fair Values of Options/Restricted Stock Granted:
Risk free interest rate	[4]	1.40%
Common stock dividend yield	[5]	3.90%
Expected volatility rate	[6]	19.70%
Average expected option life (in years)	[7]	5 years 9 months
Dividends paid for previous year		1 year
2005 to 2013 Stock Options [Member]
Compensation and Retirement Disclosure [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)		7 years
Grant date fair value of each stock option granted (in dollars per option)				$ 6.19		$ 6.75
Assumptions Used in Determining Fair Values of Options/Restricted Stock Granted:
Risk free interest rate	[4]			1.70%		1.80%
Common stock dividend yield	[5]			3.70%		4.50%
Expected volatility rate	[6]			22.40%		30.30%
Average expected option life (in years)	[7]			5 years 9 months		5 years 9 months
Time-Based Restricted Stock [Member]
Compensation and Retirement Disclosure [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		204,720		222,068		212,796
Awarded and issued	[8]	72,698		71,994		94,932
Vested	[9]	(84,212)		(85,809)		(85,660)
Forfeited		(4,225)		(3,533)
Balance of restricted stock outstanding		188,981		204,720		222,068
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value		$ 39.74		$ 35.97		$ 33.96
Awarded and issued, weighted average grant date fair value	[8]	43.59		45.91		37.76
Vested, weighted average grant date fair value	[9]	37.76		35.14		32.87
Forfeited, weighted average grant date fair value		41.96		39.94
Restricted stock outstanding, weighted average grant date fair value		42.06		39.74		35.97
Grant date fair value of restricted stock	[8]	$ 43.59		$ 45.91		$ 37.76
Fair value at grant date of restricted stock issued		$ 3,200		$ 3,300		$ 3,600
Vesting date fair value of restricted stock		$ 3,700		$ 3,900		$ 3,200
Total Return-Based Restricted Stock [Member]
Compensation and Retirement Disclosure [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 Options/Restricted Stock Granted:
Risk free interest rate	[10]	0.90%		1.00%		0.70%
Common stock dividend yield	[11]	4.10%		3.80%		4.70%
Expected volatility rate	[12]	43.10%		43.00%		43.40%
Dividends paid for previous year		1 year
Restricted Stock Activity Rollforward [Abstract]
Balance of restricted stock outstanding		195,303		207,957		133,388
Awarded and issued	[13]	64,701	[1]	118,817	[1]	74,569
Vested	[1],[14]	(71,617)		(129,762)
Forfeited		(4,663)		(1,709)
Balance of restricted stock outstanding		183,724		195,303		207,957
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value		$ 36.66		$ 35.70		$ 35.29
Awarded and issued, weighted average grant date fair value	[13]	40.87	[1]	37.64	[1]	35.58
Vested, weighted average grant date fair value	[1],[14]	36.50		31.97
Forfeited, weighted average grant date fair value		39.91		37.25
Restricted stock outstanding, weighted average grant date fair value		$ 39.82		$ 36.66		$ 35.70
Percentage of return-based restricted stock issued to officers that will vest, minimum		0.00%		0.00%		0.00%
Percentage of return-based restricted stock issued to officers that will vest, maximum		150.00%		150.00%		150.00%
Company total return, total return-based restricted stock		100.00%
Vesting percentage, total return-based restricted stock		75.00%		75.00%		75.00%
Grant date fair value of restricted stock	[13]	$ 40.87	[1]	$ 37.64	[1]	$ 35.58
Fair value at grant date of restricted stock issued		$ 2,400		$ 2,500		$ 2,700
Vesting date fair value of restricted stock		$ 3,100		$ 5,900		$ 0
Period preceding date of grant		3 months
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		$ 41.37		$ 43.77		$ 35.58
Grant date fair value of restricted stock		$ 41.37		$ 43.77		$ 35.58

[1] The 2016 and 2015 amounts include 6,647 and 61,860 additional shares, respectively, from the 2013 and 2012 plans, respectively, since the plans' payouts were in excess of the initial 100% target.

[2] The Company had 74,080 options exercisable at December 31, 2016 with a weighted average exercise price of $40.28, weighted average remaining life of 6.6 years and intrinsic value of $0.8 million. Of these exercisable options, there were no exercise prices higher than the market price of our Common Stock at December 31, 2016.

[3] The outstanding options at December 31, 2016 had a weighted average remaining life of 7.9 years.

[4] Represents the interest rate as of the grant date on US treasury bonds having the same life as the estimated life of the option grants.

[5] The dividend yield is calculated utilizing the dividends paid for the previous one-year period and the per share price of Common Stock on the date of grant.

[6] Based on the historical volatility of Common Stock over a period relevant to the related stock option grant.

[7] The average expected option life is based on an analysis of the Company's historical data.

[8] The weighted average fair value at grant date of time-based restricted stock issued during the years ended December 31, 2016, 2015 and 2014 was $3.2 million, $3.3 million and $3.6 million, respectively.

[9] The vesting date fair value of time-based restricted stock that vested during the years ended December 31, 2016, 2015 and 2014 was $3.7 million, $3.9 million and $3.2 million, respectively. Vested shares include those shares surrendered by employees to satisfy tax withholding obligations in connection with such vesting.

[10] Represents the interest rate as of the grant date on US treasury bonds having the same life as the estimated life of the total return-based restricted stock grants.

[11] The dividend yield is calculated utilizing the dividends paid for the previous one-year period and the average per share price of Common Stock during the three-month period preceding the date of grant.

[12] Based on the historical volatility of Common Stock over a period relevant to the related total return-based restricted stock grant.

[13] The fair value at grant date of total return-based restricted stock issued during the years ended December 31, 2016, 2015 and 2014 was $2.4 million, $2.5 million and $2.7 million, respectively, at target.

[14] The vesting date fair value of total return-based restricted stock that vested during the years ended December 31, 2016 and 2015 was $3.1 million and $5.9 million, respectively, based on the performance of the specific plans. Vested shares include those shares surrendered by employees to satisfy tax withholding obligations in connection with such vesting. There were no vested shares of total return-based restricted stock during the year ended December 31, 2014.