Capital Transactions (Details) (USD $)			12 Months Ended													1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Stock options and restricted stock Y	Dec. 31, 2010 Stock options and restricted stock	Dec. 31, 2009 Stock options and restricted stock	Dec. 31, 2011 Stock options Y M	Dec. 31, 2010 Stock options Y	Dec. 31, 2009 Stock options Y	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2009 Restricted Stock	Dec. 31, 2011 Restricted Stock Directors	Dec. 31, 2011 Executive Plan, Allshare Plan and 2006 Incentive Plan plan	Dec. 31, 2011 Executive Plan, Allshare Plan and 2006 Incentive Plan Stock options	May 04, 2010 2010 Incentive Plan	May 31, 2010 2010 Incentive Plan Stock options	Dec. 31, 2011 2010 Incentive Plan Stock options	Dec. 31, 2011 2010 Incentive Plan Restricted Stock
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)						4,176,673	4,586,979	4,740,695						3,754,754
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)						1.04%	1.10%	1.05%
Risk-free interest rate (as a percent)						2.08%	1.88%	1.67%
Average expected life (in years)						5.8	4.6	4.6
Expected volatility of common stock (as a percent)						40.40%	40.20%	35.10%
Forfeiture rate (as a percent)						0.00%	0.00%	1.00%
Weighted average fair value of option grants (in dollars per share)						$ 5.74	$ 4.78	$ 4.42
Granted (in shares)									249,502	248,384	227,451	26,821						222,681
Vesting period (in years)																		3 years
Number of shares
Nonvested shares at the beginning of the period (in shares)									659,263	686,586	755,127
Granted (in shares)									249,502	248,384	227,451	26,821						222,681
Vested (in shares)									(238,848)	(256,285)	(260,575)
Cancelled (in shares)									(58,315)	(19,422)	(35,417)
Nonvested shares at the end of the period (in shares)									611,602	659,263	686,586
Weighted Average Grant-Date Fair Value
Nonvested shares at the beginning of the period (in dollars per share)									$ 18.97	$ 23.13	$ 25.50
Granted (in dollars per share)									$ 15.51	$ 14.49	$ 15.24	$ 15.51						$ 15.51
Vested (in dollars per share)									$ 25.80	$ 25.51	$ 22.94
Cancelled (in dollars per share)									$ 15.71	$ 21.68	$ 24.10
Nonvested shares at the end of the period (in dollars per share)									$ 15.08	$ 18.97	$ 23.13
Compensation expenses
Equity-based compensation expense			$ 5,400,000	$ 6,400,000	$ 7,900,000
Total unrecognized compensation cost			5,400,000
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)						4,586,979	4,740,695	4,470,734						3,754,754
Granted (in shares)						327,617	320,458	457,397									327,617
Exercised (in shares)						(5,941)	(4,821)	(13,011)
Cancelled (in shares)						(731,982)	(469,353)	(174,425)
Outstanding at the end of the period (in shares)						4,176,673	4,586,979	4,740,695						3,754,754
Exercisable (in shares)						3,310,143	3,468,223
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)						$ 19.96	$ 20.37	$ 20.90
Granted (in dollars per share)						$ 15.45	$ 14.49	$ 15.24
Exercised (in dollars per share)						$ 10.57	$ 10.57	$ 14.64
Cancelled (in dollars per share)						$ 24.73	$ 20.46	$ 19.66
Outstanding at the end of the period (in dollars per share)						$ 19.26	$ 19.96	$ 20.37
Exercisable (in dollars per share)						$ 20.35	$ 20.52
Weighted Average Remaining Contractual Term
Outstanding, Weighted Average Remaining Contractual Term (in years)						2.7	3.3
Exercisable, Weighted Average Remaining Contractual Term (in years)						2.1	2.7
Aggregate Intrinsic Value
Total intrinsic value of options exercised						$ 31,000	$ 19,000	$ 38,000
Non-vested stock options
Non-vested shares at beginning of year (in shares)						1,118,756
Granted (in shares)						327,617	320,458	457,397									327,617
Vested (in shares)						(340,900)
Cancelled (in shares)						(238,943)
Non-vested shares at end of year (in shares)						866,530	1,118,756
Weighted Average Grant-Date Fair Value
Non-vested shares at beginning of year (in dollars per share)						$ 5.10
Granted (in dollars per share)						$ 5.74	$ 4.78	$ 4.42
Vested (in dollars per share)						$ 6.34
Cancelled (in dollars per share)						$ 5.02
Non-vested shares at end of year (in dollars per share)						$ 4.82	$ 5.10