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Stock-Based Compensation (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense related to stock awards	$ 6,800,000		$ 6,500,000
Shares outstanding above stock price (in shares)	244,900
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding at beginning of period, Shares	920,505
Options, Granted, Shares	0
Options, Exercised, Shares	(215,945)
Options, Forfeited, Shares	(1,000)
Options, Expired, Shares	(66,201)
Options, Outstanding at end of period, Shares	637,359
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options, Outstanding at beginning of period, Weighted-Average Exercise Price (in dollars per share)	$ 20.39
Options, Granted, Weighted-Average Exercise Price (in dollars per share)	0.00
Options, Exercised, Weighted-Average Exercise Price (in dollars per share)	19.98
Options, Forfeited, Weighted-Average Exercise Price (in dollars per share)	30.50
Options, Expired, Weighted-Average Exercise Price (in dollars per share)	27.90
Options, Outstanding at end of period, Weighted-Average Exercise Price (in dollars per share)	19.54
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value of options granted (in dollars per share)	$ 0.00	$ 0.00
Total fair value of options that vested (in thousands)	$ 0	$ 0
Total intrinsic value of options exercised (in thousands)	$ 1,814,000	$ 2,199,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected quarterly dividends per share	$ 0.200	$ 0.185
Risk-free interest rate	0.92%	0.62%
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Restricted Stock, Outstanding at beginning of period, Shares	258,770
Restricted Stock, Granted, Shares	340,020
Restricted Stock, Exercised, Shares	(349,468)
Restricted Stock, Forfeited, Shares	(4,061)
Restricted Stock, Outstanding at end of period, Shares	245,261
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted Stock, Outstanding at beginning of period, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 22.31
Restricted Stock, Granted, Weighted-Average Grant Date Fair Value (in dollars per share)	20.34	$ 21.27
Restricted Stock, Exercised, Weighted-Average Grant Date Fair Value (in dollars per share)	18.61
Restricted Stock, Forfeited, Weighted-Average Grant Date Fair Value (in dollars per share)	24.81
Restricted Stock, Outstanding at end of period, Weighted-Average Grant Date Fair Value (in dollars per share)	24.81
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value (in dollars per share)	$ 20.34	$ 21.27
Total fair value of restricted shares that vested (in thousands)	$ 6,503,000	$ 4,929,000
Market-Based Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.00%	0.64%
Dividend yield	2.87%	2.82%
Expected volatility	18.73%	25.11%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of stock options outstanding	$ 6,000,000
Weighted-average remaining contract life	2 years 4 months 17 days
Executive [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	179,845
Share-based compensation, weighted percentage assigned to achieving market targets	60.00%
Share-based compensation, weighted percentage assigned to achieving performance targets	40.00%
Share-based compensation, maximum number of shares awarded in year 1 (in shares)	180,970
Share-based compensation, maximum number of shares awarded in year 2 (in shares)	165,628
Share-based compensation, maximum number of shares awarded in year 3 (in shares)	168,258
Performance period	3 years
Chairman, President, and Chief Executive Officer [Member] | Achieves a specified improvement in total shareholder return at the end of 2016 compared to 2011 and she remains an employee [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received if achieves specified improvement in total shareholders return (in shares)	135,000
Chairman, President, and Chief Executive Officer [Member] | Achieves a specified improvement in total shareholder return at the end of 2014 compared to 2011 and she remains an employee [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received if achieves specified improvement in total shareholders return (in shares)	35,000
Chairman, President, and Chief Executive Officer [Member] | Achieves a specific performance target by the end of 2019 and she remains an employee [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received if achieves specified improvement in total shareholders return (in shares)	53,859
Chairman, President, and Chief Executive Officer [Member] | Achieves a specific performance target by the end of 2017 and she remains an employee [Member] [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares received if achieves specified improvement in total shareholders return (in shares)	17,953
Executive Vice President and Chief Financial Officer [Member] | Achieved performance target for 2015 and 2016 [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, purchase price of common stock	$ 100,000
Executive Vice President and Chief Financial Officer [Member] | Achieved performance target for 2015, 2016 and 2017 [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, purchase price of common stock	$ 275,000
Performance Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Vesting rate	100.00%

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