Capital Transactions (Details) (USD $)	12 Months Ended														0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Stock options and restricted stock	Dec. 31, 2013 Stock options	Dec. 31, 2012 Stock options	Dec. 31, 2011 Stock options	Dec. 31, 2013 Restricted Stock	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2013 Restricted Stock Directors	Dec. 31, 2013 Executive Plan, All share Plan and 2006 Incentive Plan item	Dec. 31, 2013 Executive Plan, All share Plan and 2006 Incentive Plan Stock options	May 04, 2010 2010 Incentive Plan	May 04, 2010 2010 Incentive Plan Stock options	Dec. 31, 2013 2010 Incentive Plan Stock options	Dec. 31, 2013 2010 Incentive Plan Restricted Stock
Capital Transactions
Stock based compensation expense	$ 4,363,000	$ 4,693,000	$ 5,365,000
Preferred Stock
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock outstanding (in shares)	0
Stock Compensation
Number of shares authorized														5,150,000
Minimum incentive stock option exercise price, expressed as a percentage of common stock grant date market value															100.00%
Number of stock option plans												3
Options outstanding (in shares)					3,407,575	3,653,859	4,176,673						2,613,415
Additional shares of common stock available for issuance	0
Assumptions used to determine value of the shares purchased under the stock purchase plan using Black-Scholes option pricing model
Expected annual dividend rate (as a percent)					1.21%	1.23%	1.04%
Risk-free interest rate (as a percent)					0.92%	0.81%	2.08%
Average expected life (in years)					6 years	5 years 7 months 6 days	5 years 9 months 18 days
Expected volatility of common stock (as a percent)					44.60%	40.90%	40.40%
Forfeiture rate (as a percent)					0.00%	0.00%	0.00%
Granted (in dollars per share)					$ 5.04	$ 4.43	$ 5.74
Granted (in shares)								312,104	318,139	249,502	29,453						282,651
Vesting period																	3 years
Number of shares
Nonvested shares at the beginning of the period (in shares)								698,885	611,602	659,263
Granted (in shares)								312,104	318,139	249,502	29,453						282,651
Vested (in shares)								(231,465)	(212,841)	(238,848)
Cancelled (in shares)								(45,933)	(18,015)	(58,315)
Nonvested shares at the end of the period (in shares)								733,591	698,885	611,602
Weighted Average Grant-Date Fair Value
Nonvested shares at the beginning of the period (in dollars per share)								$ 14.21	$ 15.08	$ 18.97
Granted (in dollars per share)								$ 13.41	$ 13.04	$ 15.51	$ 13.41						$ 13.24
Vested (in dollars per share)								$ 14.35	$ 14.95	$ 25.80
Cancelled (in dollars per share)								$ 13.69	$ 14.20	$ 15.71
Nonvested shares at the end of the period (in dollars per share)								$ 13.79	$ 14.21	$ 15.08
Compensation expenses
Total unrecognized compensation cost				4,900,000
Unrecognized compensation cost recognized over a weighted average period (in years)				1 year 8 months 12 days
Period from grant date after which stock options become exercisable, minimum (in months)					6 months
Period from grant date within which incentive stock options are exercisable, maximum (in years)					10 years
Number of Options
Outstanding at the beginning of the period (in shares)					3,653,859	4,176,673	4,586,979						2,613,415
Granted (in shares)					173,560	200,115	327,617									173,560
Exercised (in shares)					(75,080)	(179,204)	(5,941)
Cancelled (in shares)					(344,764)	(543,725)	(731,982)
Outstanding at the end of the period (in shares)					3,407,575	3,653,859	4,176,673						2,613,415
Exercisable (in shares)					2,818,464	3,031,825
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)					$ 18.44	$ 19.26	$ 19.96
Granted (in dollars per share)					$ 13.24	$ 13.06	$ 15.45
Exercised (in dollars per share)					$ 10.91	$ 10.57	$ 10.57
Cancelled (in dollars per share)					$ 20.67	$ 25.35	$ 24.73
Outstanding at the end of the period (in dollars per share)					$ 17.99	$ 18.44	$ 19.26
Exercisable (in dollars per share)					$ 18.83	$ 19.28
Weighted Average Remaining Contractual Term
Outstanding, Weighted Average Remaining Contractual Term (in years)					1 year 9 months 18 days	2 years 3 months 18 days
Exercisable, Weighted Average Remaining Contractual Term (in years)					1 year 1 month 6 days	1 year 9 months 18 days
Aggregate Intrinsic Value
Total intrinsic value of options exercised					$ 172,000	$ 191,000	$ 31,000
Non-vested stock options
Non-vested shares at beginning of year (in shares)					622,034
Granted (in shares)					173,560	200,115	327,617									173,560
Vested (in shares)					(206,483)
Non-vested shares at end of year (in shares)					589,111	622,034
Weighted Average Grant-Date Fair Value
Non-vested shares at beginning of year (in dollars per share)					$ 4.99
Granted (in dollars per share)					$ 5.04	$ 4.43	$ 5.74
Vested (in dollars per share)					$ 4.78
Non-vested shares at end of year (in dollars per share)					$ 5.07	$ 4.99