Stock Compensation Plans (Narrative) (Details) (USD $)	12 Months Ended						12 Months Ended			12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Restricted Stock [Member] years	Dec. 31, 2011 1997 Plan [Member] years	Dec. 31, 2011 1997 Non-Employee Stock Option Director Plan [Member]	Dec. 31, 2011 2004 Plan [Member]	Dec. 31, 2011 2009 Plan [Member]	Dec. 31, 2011 2010 Change In Plan [Member] years	Dec. 31, 2009 Director's Plan, Per Director [Member]	Dec. 31, 2008 Director's Plan, Per Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted awards, authorized					1,400,000	250,000	1,750,000	1,781,546
Granted stock, outstanding							5,251
Common stock, outstanding	865,445	1,098,859			28,583	3,000	397,170	436,692
Exercise price, lower range				$ 13.04	$ 1.68		$ 12.50	$ 17.04
Exercise price, upper range				$ 24.30	$ 27.40		$ 31.06	$ 39.33
Vesting period, years	three			3	3			three
Shares, Granted	32,045
Options outstanding, exercise price	$ 26.72	$ 21.37				$ 21.56
Weighted average remaining contractual term	4.7			10	10				7
Allocated Share-based Compensation Expense	$ 2,756,000	$ 2,416,000	$ 2,449,000
Weighted-average grant-date fair value	$ 14.15	$ 9.30	$ 5.08
Aggregate intrinsic value, Options exercised	10,400,000	700,000	50,000
Total fair value of stock options using the Black-Scholes option pricing model	1,600,000	1,700,000	1,700,000
Stock-based compensation expense, non-vested stock-based	4,400,000
Expected recognition period (years)	2.0
The terms for number of shares to be granted upon election											3,400
The terms for number of shares to be granted to director											2,200
The terms for value of shares to be granted upon election										100,000
The terms for value of shares to be granted to director										$ 70,000