Stock-Based Compensation Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015	Feb. 28, 2015	Jan. 01, 2015	Mar. 31, 2012
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specified improvement in total shareholder return at the end of 2016 compared to 2011 and she remains an employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)							135,000
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specified improvement in total shareholder return at the end of 2014 compared to 2011 and she remains an employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)							35,000
Number of shares approved upon meeting target (in shares)					35,000
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specific performance target by the end of 2019 and she remains an employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)				53,859
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specific performance target by the end of 2017 and she remains an employee [Member] [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)				17,953
Executive Vice President and Chief Financial Officer [Member] | Common Stock [Member] | Achieved performance target for 2015 and 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Share-based compensation arrangement by share-based payment award, purchase price of common stock						$ 100,000
Executive Vice President and Chief Financial Officer [Member] | Common Stock [Member] | Achieved performance target for 2015, 2016 and 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Share-based compensation arrangement by share-based payment award, purchase price of common stock						$ 275,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Restricted Stock, at Beginning of period, Shares	258,770
Restricted Stock, at Beginning of period, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 22.31
Restricted Stock, Granted, Shares	340,020
Restricted Stock, Granted, Fair Value (in dollars per share)	$ 20.34	$ 21.27	$ 20.03
Restricted Stock, Vested, Shares	(349,635)
Restricted Stock, Vested, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 18.61
Restricted Stock, Forfeited, Shares	(4,061)
Restricted Stock, Forfeited, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 24.81
Restricted Stock, at end of period, Shares	245,094	258,770
Restricted Stock, at end of period, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 24.81	$ 22.31
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value (in dollars per share)	$ 20.34	$ 21.27	$ 20.03
Total fair value of restricted shares that vested	$ 6,507,000	$ 4,933,000	$ 4,395,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Outstanding at beginning of period, Shares	920,505
Options, Outstanding at beginning of period, Weighted-Average Exercise Price (in dollars per share)	$ 20.39
Options, Granted, Shares	0
Options, Granted, Weighted-Average Exercise Price (in dollars per share)	$ 0.00
Options, Exercised, Shares	(280,612)
Options, Exercised, Weighted-Average Exercise Price (in dollars per share)	$ 20.13
Options, Forfeited, Shares	(1,000)
Options, Forfeited, Weighted-Average Exercise Price (in dollars per share)	$ 30.50
Options, Expired, Shares	(69,551)
Options, Expired, Weighted-Average Exercise Price (in dollars per share)	$ 28.02
Options, Outstanding at end of period, Shares	569,342	920,505
Options, Outstanding at end of period, Weighted-Average Exercise Price (in dollars per share)	$ 19.35	$ 20.39
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Aggregate intrinsic value of stock options outstanding	$ 6,400,000
Weighted average remaining contract life	2 years 3 months 7 days
Exercise price of stock options that are greater than the closing price (in shares)	2,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value options granted (in dollars per share)	$ 0.00	$ 0.00	$ 0.00
Total fair value of options that vested	$ 0	$ 0	$ 625,000
Total intrinsic value of options exercised	$ 2,350,000	$ 2,473,000	$ 2,721,000
Performance Shares [Member] | Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares excluded from shares outstanding (in shares)	79,619	179,845
Share based compensation, weighted percentage assigned to achieving market targets	60.00%	60.00%
Share based compensation, weighted percentage assigned to achieving performance targets	40.00%	40.00%
Shares approved, maximum number of shares available in year two (in shares)	165,628
Shares approved, maximum number of shares available in year three (in shares)	168,258