Share-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Share-Based Compensation
Total shares authorized	4,700,000
Shares available for future grants of stock options or restricted stock	3,200,000
Compensation Expense	$ 6,216,000	$ 3,841,000	$ 3,552,000
Income Tax Benefit	2,668,000	1,648,000	1,560,000
Assumptions:
Average Risk Free Interest Rate (as a percent)	0.96%
Average Expected Volatility (as a percent)	39.94%
Expected Dividend Yield (as a percent)	3.87%
Expected Life (in years)	5.22
Restricted Stock
Share-based compensation
Vesting period, low end of range (in years)	P1Y
Vesting period, high end of range (in years)	P5Y
Restricted Stock
Unrecognized compensation cost related to unvested restricted stock	1,300,000
Weighted average period during which unrecognized compensation cost is expected to be recognized (in years)	1.5
Number of Shares
Unvested at the beginning of the period (in shares)	126,885	143,965	225,995
Granted (in shares)	20,831	88,404	10,129
Vested (in shares)	(65,226)	(104,128)	(90,382)
Forfeited (in shares)	(1,648)	(1,356)	(1,777)
Unvested at the end of the period (in shares)	80,842	126,885	143,965
Weighted Average Grant Date Fair Value
Unvested at the beginning of the period (in dollars per share)	$ 52.34	$ 50.84	$ 52.05
Granted (in dollars per share)	$ 47.58	$ 52.50	$ 36.26
Vested (in dollars per share)	$ 52.28	$ 50.40	$ 52.21
Forfeited (in dollars per share)	$ 52.69	$ 53.42	$ 51.78
Unvested at the end of the period (in dollars per share)	$ 51.15	$ 52.34	$ 50.84
Grant Date Fair Value of Restricted Stock that Vested During the Year
Vested (in dollars)	3,410,000	5,248,000	4,719,000
Stock Options
Share-based compensation
Expiration period from the date of grant (in years)	P10Y
Weighted Average Fair Value of Stock Options Granted During the Year (in dollars per share)	$ 10.47
Stock Options Granted During the Year (in shares)	341,629
Stock Options
Outstanding at the beginning of the period (in shares)	913,618
Granted (in shares)	341,629
Exercised (in shares)	(217,818)
Expired (in shares)	(16,239)
Outstanding at the end of the period (in shares)	1,021,190	913,618
Vested and Exercisable at the end of the period (in shares)	679,561
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 36.18
Granted (in dollars per share)	$ 42.22
Exercised (in dollars per share)	$ 27.75
Expired (in dollars per share)	$ 43.56
Outstanding at the end of the period (in dollars per share)	$ 39.88	$ 36.18
Vested and Exercisable at the end of period (in dollars per share)	$ 38.71
Weighted Average Remaining Contractual Term
Outstanding at the end of the period (in years)	4.7
Vested and Exercisable at the end of period (in years)	2.0
Aggregate Intrinsic Value
Outstanding at the end of the period	6,043,000
Vested and Exercisable at the end of the period	5,267,000
Stock options activity
Intrinsic Value of Stock Options Exercised	3,790,000	9,507,000	1,688,000
Cash Received from Stock Options Exercised	6,044,000	9,628,000	2,736,000
Tax Benefits Realized from Stock Options Exercised	888,000	2,983,000	278,000
Total Fair Value of Stock Options that Vested	$ 3,578,000		$ 96,000