Stock and Incentive Compensation Plans (Details) (USD $)	12 Months Ended																			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Price Range 19.41-22.64 [Member]	Dec. 31, 2011 Price Range 22.64-25.88 [Member]	Dec. 31, 2011 Price Range 29.11-32.35 [Member]	Dec. 31, 2011 Performance Based Award [Member]	Dec. 31, 2010 Performance Based Award [Member]	Dec. 31, 2009 Performance Based Award [Member]	Dec. 31, 2011 Time Vested Award [Member]	Dec. 31, 2010 Time Vested Award [Member]	Dec. 31, 2009 Time Vested Award [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member] Performance Based Award [Member]	Dec. 31, 2011 Restricted Stock [Member] Performance Based Excess Time-Vested [Member]	Dec. 31, 2011 Restricted Stock [Member] Time Vested Award [Member]	May 10, 2011 Restricted Stock Units (RSUs) [Member] Performance Based Award [Member]	Dec. 31, 2011 Stock option-based awards [Member]	Dec. 31, 2010 Stock option-based awards [Member]	Dec. 31, 2009 Stock option-based awards [Member]	Dec. 31, 2011 2005 Stock and Incentive Compensation Plan [Member]	Dec. 31, 2010 1997 Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance (in shares)																							5,030,943
Stock options, vesting percentage per year (in hundredths)																							20.00%
Stock and incentive compensation plan, contractual term (in years)																							7Y	10Y
Vesting period																3 Y	3 Y	36 M						4Y
Options [Roll Forward]
Outstanding, beginning of year (in shares)																				1,311,925	1,531,925	1,796,174
Granted (in shares)																				0	0	0
Exercised (in shares)																				(69,525)	(188,550)	(154,500)
Expired (in shares)																				(36,000)	(29,350)	(98,749)
Forfeited (in shares)																				(1,300)	(2,100)	(11,000)
Outstanding, end of year (in shares)																				1,205,100	1,311,925	1,531,925
Exercisable, end of year (in shares)																				1,205,100	1,270,085	1,392,355
Weighted average option price [Abstract]
Outstanding, beginning of year (in dollars per share)																				$ 27.03	$ 26.27	$ 25.57
Granted (in dollars per share)																				$ 0	$ 0	$ 0
Exercised (in dollars per share)																				$ 21.68	$ 20.65	$ 19.35
Expired (in dollars per share)																				$ 27.71	$ 28.22	$ 23.75
Forfeited (in dollars per share)																				$ 31.55	$ 31.55	$ 30.71
Outstanding, end of year (in dollars per share)																				$ 27.31	$ 27.03	$ 26.27
Exercisable, end of year (in dollars per share)																				$ 27.31	$ 26.88	$ 25.87
Aggregate intrinsic value [Abstract]
Outstanding, end of year																				$ 44,365	$ 394,341	$ 424,029
Exercisable, end of year																				44,365	394,341	424,029
Total intrinsic value of options exercised																				144,000	569,000	426,000
Shares [Roll Forward]
Nonvested shares, beginning of year (in shares)							210,797	229,227	212,464	343,469	291,999	139,943
Granted (in shares)							53,863	55,787	79,631	157,178	146,605	187,196
Released from restriction (in shares)							(84,338)	(73,862)	(62,038)	(160,447)	(90,372)	(29,516)
Forfeited (in shares)							(901)	(355)	(830)	(5,844)	(4,763)	(5,624)
Nonvested shares, end of year (in shares)							179,421	210,797	229,227	334,356	343,469	291,999
Weighted-average grant date fair value [Abstract]
Nonvested shares, beginning of year (in dollars per share)							$ 20.30	$ 25.52	$ 27.60	$ 20.33	$ 25.50	$ 27.58
Granted (in dollars per share)							$ 25.40	$ 23.05	$ 17.75	$ 24.15	$ 22.44	$ 19.36
Released from restriction (in dollars per share)							$ 20.00	$ 27.68	$ 26.39	$ 20.46	$ 23.91	$ 28.56
Forfeited (in dollars per share)							$ 23.82	$ 25.30	$ 24.74	$ 20.17	$ 20.52	$ 24.72
Nonvested shares, end of year (in dollars per share)							$ 20.30	$ 20.30	$ 25.52	$ 21.04	$ 20.33	$ 25.50
ROATE Performance measure (in hundredths)																100.00%
Compensation expense for all stock incentive plans [Abstract]
Recognized compensation expense	3,974,000	5,520,000	4,933,000				855,000	1,004,000	1,224,000	2,835,000	3,390,000	2,659,000	184,000	696,000	376,000					100,000	430,000	674,000
Unrecognized compensation expense		$ 5,841,000					$ 887,000			$ 4,954,000			$ 0							$ 0
Weighted average life of unrecognized compensation expense (in years)							1.67			2.94			0							0
RSU award share price (in dollars per share)																			$ 23.65
Options outstanding [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)				$ 22.64	$ 25.88	$ 29.11
Range of Exercise Prices, upper limit (in dollars per share)				$ 25.88	$ 29.11	$ 32.35
Outstanding, end of period (in shares)	1,205,100			438,050	553,900	213,150
Weighted- Average Remaining Years To Expiration (in years)	1.2			0.8	1.4	1.4
Weighted- Average Exercise Price (in dollars per share)	$ 27.31			$ 24.76	$ 27.72	$ 31.48
Options exercisable [Abstract]
Exercisable, end of period (in shares)	1,205,100			438,050	553,900	213,150
Exercisable Weighted- Average Remaining Years To Expiration (in years)	1.2			0.8	1.4	1.4
Exercisable Weighted- Average Exercise Price (in dollars per share)	$ 27.31			$ 24.76	$ 27.72	$ 31.48