Employee Benefit Plans (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
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		702,228		592,321
Possible future share issuance authorized under equity incentive plans		3,084,158		1,382,406
Total shares reserved for future issuance		3,786,386		1,974,727
Possible future share issuance authorized under equity incentive plan restricted stock		1,100,000
Stock-based compensation expense		$ 6,884		$ 6,939		$ 6,899
Total unrecognized stock-based compensation costs		$ 4,900
Weighted average remaining term of vesting periods (in years)		2 years 3 months 18 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		1,200		1,100
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
2009 and prior retirement plan immediate vesting percentage		100.00%
Deferred Compensation [Abstract]
Marketable securities of non-qualified deferred compensation plan fair value disclosure		$ 2,736		3,635		3,996
Non Qualified Deferred Compensation Obligation Fair Value Disclosure [Roll Forward]
Beginning deferred compensation liability		3,635		3,996		3,354
Mark to market adjustment to deferred compensation (in general and administrative expenses)		(32)		235		803
Distributions from deferred compensation plans		(867)		(596)		(161)
Ending deferred compensation liability		$ 2,736		$ 3,635		$ 3,996
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		29,496		28,682		27,250
Employee Stock Purchase Plan Market Percentage Discount		15.00%
Discount on newly issued shares expensed as additional compensation		$ 200		$ 200		$ 200
Stock Options [Member]
Stock Option Activity Rollforward [Abstract]
Balance of options outstanding		577,321	[1],[2]	874,382		1,129,309
Options granted		197,408		190,330		168,700
Options canceled		(3,829)		(134,628)
Options exercised		(83,672)		(352,763)		(423,627)
Balance of options outstanding		687,228	[1],[2]	577,321	[1],[2]	874,382
Stock Option Activity, Weighted Average Exercise Price Rollforward [Abstract]
Options outstanding, weighted average exercise price		$ 34.92		$ 32.24		$ 30.10
Options granted, weighted average exercise price		45.61		37.90		36.50
Options canceled, weighted average exercise price		40.21		41.93
Options exercised, weighted average exercise price		34.89		27.21		28.22
Options outstanding, weighted average exercise price		$ 37.97	[1],[2]	$ 34.92		$ 32.24
Weighted average remaining life of outstanding options		6 years 1 month 6 days
Options exercisable		218,816
Weighted average exercise price		$ 33.03
Weighted average remaining life		3 years 2 months 12 days
Intrinsic value		$ 2,300
Cash received or receivable from options exercised		3,300		$ 11,100		$ 12,500
Total instrinsic value of options exercised		900		5,000		3,900
Total intrinsic value of options outstanding		$ 4,300		$ 5,400		$ 4,300
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)		$ 6.19
Assumptions Used in Determining Fair Values of Options/Restricted Stock Granted:
Risk free interest rate	[3]	1.70%
Common stock dividend yield	[4]	3.70%
Expected volatility rate	[5]	22.40%
Average expected option life (in years)	[6]	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)				$ 6.75		$ 6.50
Assumptions Used in Determining Fair Values of Options/Restricted Stock Granted:
Risk free interest rate	[3]			1.80%		1.00%
Common stock dividend yield	[4]			4.50%		4.70%
Expected volatility rate	[5]			30.30%		32.40%
Average expected option life (in years)	[6]			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		222,068		212,796		222,502
Awarded and issued	[7]	71,994		94,932		86,144
Vested	[8]	(85,809)		(85,660)		(94,037)
Forfeited		(3,533)				(1,813)
Balance of restricted stock outstanding		204,720		222,068		212,796
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value		$ 35.97		$ 33.96		$ 30.31
Awarded and issued, weighted average grant date fair value	[7]	45.91		37.76		36.64
Vested, weighted average grant date fair value	[8]	35.14		32.87		27.80
Forfeited, weighted average grant date fair value		39.94				36.01
Restricted stock outstanding, weighted average grant date fair value		39.74		35.97		33.96
Grant date fair value of restricted stock	[7]	$ 45.91		$ 37.76		$ 36.64
Fair value at grant date of restricted stock issued		$ 3,300		$ 3,600		$ 3,200
Vesting date fair value of restricted stock		$ 3,900		$ 3,200		$ 3,400
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	[9]	1.00%		0.70%		0.40%
Common stock dividend yield	[10]	3.80%		4.70%		4.90%
Expected volatility rate	[11]	43.00%		43.40%		43.40%
Dividends paid for previous year		1 year
Restricted Stock Activity Rollforward [Abstract]
Balance of restricted stock outstanding		207,957		133,388		125,288
Awarded and issued	[13]	118,817	[12]	74,569		65,486
Vested	[14]	(129,762)	[12]			(41,863)
Forfeited		(1,709)				(15,523)
Balance of restricted stock outstanding		195,303		207,957		133,388
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Restricted stock outstanding, weighted average grant date fair value		$ 35.70		$ 35.29		$ 32.87
Awarded and issued, weighted average grant date fair value	[13]	37.64	[12]	35.58		31.73
Vested, weighted average grant date fair value	[14]	31.97	[12]			24.75
Forfeited, weighted average grant date fair value		37.25				24.75
Restricted stock outstanding, weighted average grant date fair value		$ 36.66		$ 35.70		$ 35.29
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%		50.00%
Grant date fair value of restricted stock	[13]	$ 37.64	[12]	$ 35.58		$ 31.73
Fair value at grant date of restricted stock issued		$ 2,500		$ 2,700		$ 2,100
Vesting date fair value of restricted stock		$ 5,900		$ 0		$ 1,500
Period preceding date of grant		3 months
2012 Plan [Member]
Restricted Stock Activity Rollforward [Abstract]
Awarded and issued	[12]	61,860
Vested	[12]	(61,860)
Total Return-Based Restricted Stock 2015 Issuance [Member]
Restricted Stock Activity, Weighted Average Grant Date Fair Value Rollforward [Abstract]
Awarded and issued, weighted average grant date fair value		$ 43.77
Grant date fair value of restricted stock		$ 43.77

[1] The Company had 218,816 options exercisable at December 31, 2015 with a weighted average exercise price of $33.03, weighted average remaining life of 3.2 years and intrinsic value of $2.3 million. Of these exercisable options, there were no exercise prices higher than the market price of our Common Stock at December 31, 2015.

[2] The outstanding options at December 31, 2015 had a weighted average remaining life of 6.1 years.

[3] 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.

[4] 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.

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

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

[7] The weighted average fair value at grant date of time-based restricted stock issued during the years ended December 31, 2015, 2014 and 2013 was $3.3 million, $3.6 million and $3.2 million, respectively.

[8] The vesting date fair value of time-based restricted stock that vested during the years ended December 31, 2015, 2014 and 2013 was $3.9 million, $3.2 million and $3.4 million, respectively. Vested shares include those shares surrendered by employees to satisfy tax withholding obligations in connection with such vesting.

[9] 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.

[10] 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.

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

[12] The 2015 amounts include 61,860 additional shares from the 2012 plan since the plan's payout was in excess of the initial 100% target.

[13] The fair value at grant date of total return-based restricted stock issued during the years ended December 31, 2015, 2014 and 2013 was $2.5 million, $2.7 million and $2.1 million, respectively, at target.

[14] The vesting date fair value of total return-based restricted stock that vested during the years ended December 31, 2015 and 2013 was $5.9 million and $1.5 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.