Capital Transactions (Details) (USD $)	12 Months Ended														0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Stock options and restricted stock Y	Dec. 31, 2012 Stock options Y M	Dec. 31, 2011 Stock options Y	Dec. 31, 2010 Stock options Y	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2012 Restricted Stock Directors	Dec. 31, 2012 Executive Plan, All share Plan and 2006 Incentive Plan aircraft	Dec. 31, 2012 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, 2012 2010 Incentive Plan Stock options	Dec. 31, 2012 2010 Incentive Plan Restricted Stock
Capital Transactions
Stock based compensation expense	$ 4,693,000	$ 5,365,000	$ 6,428,000
Preferred Stock
Preferred stock, shares authorized	5,000,000	5,000,000
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)					3,653,859	4,176,673	4,586,979						3,031,825
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)					1.23%	1.04%	1.10%
Risk-free interest rate (as a percent)					0.81%	2.08%	1.88%
Average expected life (in years)					5.6	5.8	4.6
Expected volatility of common stock					40.90%	40.40%	40.20%
Forfeiture rate (as a percent)					0.00%	0.00%	0.00%
Weighted average fair value of option grants (in dollars per share)					$ 4.43	$ 5.74	$ 4.78
Granted (in shares)								318,139	249,502	248,384	27,874						290,265
Vesting period																	3 years
Number of shares
Nonvested shares at the beginning of the period (in shares)								611,602	659,263	686,586
Granted (in shares)								318,139	249,502	248,384	27,874						290,265
Vested (in shares)								(212,841)	(238,848)	(256,285)
Cancelled (in shares)								(18,015)	(58,315)	(19,422)
Nonvested shares at the end of the period (in shares)								698,885	611,602	659,263
Weighted Average Grant-Date Fair Value
Nonvested shares at the beginning of the period (in dollars per share)								$ 15.08	$ 18.97	$ 23.13
Granted (in dollars per share)								$ 13.04	$ 15.51	$ 14.49	$ 13.06						$ 13.06
Vested (in dollars per share)								$ 14.95	$ 25.80	$ 25.51
Cancelled (in dollars per share)								$ 14.20	$ 15.71	$ 21.68
Nonvested shares at the end of the period (in dollars per share)								$ 14.21	$ 15.08	$ 18.97
Compensation expenses
Total unrecognized compensation cost				4,900,000
Unrecognized compensation cost recognized over a weighted average period (in years)				1.7
Period from grant date after which stock options become exercisable, minimum (in months)					6
Period from grant date within which incentive stock options are exercisable, maximum (in years)					10
Number of Options
Outstanding at the beginning of the period (in shares)					4,176,673	4,586,979	4,740,695						3,031,825
Granted (in shares)					200,115	327,617	320,458									200,115
Exercised (in shares)					(179,204)	(5,941)	(4,821)
Cancelled (in shares)					(543,725)	(731,982)	(469,353)
Outstanding at the end of the period (in shares)					3,653,859	4,176,673	4,586,979						3,031,825
Exercisable (in shares)					3,031,825	3,310,143
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)					$ 19.26	$ 19.96	$ 20.37
Granted (in dollars per share)					$ 13.06	$ 15.45	$ 14.49
Exercised (in dollars per share)					$ 10.57	$ 10.57	$ 10.57
Cancelled (in dollars per share)					$ 25.35	$ 24.73	$ 20.46
Outstanding at the end of the period (in dollars per share)					$ 18.44	$ 19.26	$ 19.96
Exercisable (in dollars per share)					$ 19.28	$ 20.35
Weighted Average Remaining Contractual Term
Outstanding, Weighted Average Remaining Contractual Term (in years)					2.3	2.7
Exercisable, Weighted Average Remaining Contractual Term (in years)					1.8	2.1
Aggregate Intrinsic Value
Total intrinsic value of options exercised					$ 191,000	$ 31,000	$ 19,000
Non-vested stock options
Non-vested shares at beginning of year (in shares)					866,530
Granted (in shares)					200,115	327,617	320,458									200,115
Vested (in shares)					(444,611)
Non-vested shares at end of year (in shares)					622,034	866,530
Weighted Average Grant-Date Fair Value
Non-vested shares at beginning of year (in dollars per share)					$ 4.82
Granted (in dollars per share)					$ 4.43	$ 5.74	$ 4.78
Vested (in dollars per share)					$ 4.42
Non-vested shares at end of year (in dollars per share)					$ 4.99	$ 4.82