Share-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended									0 Months Ended
	Dec. 31, 2011 year	Dec. 31, 2010 year	Dec. 31, 2009 year	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Jan. 03, 2012 Stock Award [Member]	Feb. 09, 2012 Stock Award [Member] Restricted Stock [Member]
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Share-based compensation incurred	$ 8,247	$ 6,487	$ 7,139	$ 7,308	$ 5,232	$ 5,718	$ 939	$ 1,255	$ 1,421
Capitalized share-based compensation	(663)	(745)	(945)
Share-based compensation expense	7,584	5,742	6,194
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Volatility		30.00%	28.60%
Expected dividend yield		4.00%	3.60%
Expected term (in years)		4.3	4.9
Risk free interest rate		1.90%	1.60%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of year (in shares)	757,424
Outstanding at the beginning of year, Weighted-Average Exercise Price (in dollars per share)	$ 62.09
Granted (in shares)	0
Granted, Weighted-Average Exercise Price (in dollars per share)	$ 0.00
Exercised (in shares)	(237,271)
Exercised, Weighted-Average Exercise Price (in dollars per share)	$ 64.02
Forfeited or expired (in shares)	(2,500)
Forfeited or Expired, Weighted-Average Exercise Price (in dollars per share)	$ 88.60
Outstanding at the end of year (in shares)	517,653	757,424
Outstanding at the end of year, Weighted-Average Exercise Price (in dollars per share)	$ 61.08	$ 62.09
Outstanding at the end of year, Weighted-Average Remaining Contractual Term (in years)	5.9
Outstanding at the end of year, Intrinsic Value	15,423
Exercisable at the end of year (in shares)	286,054
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 64.49
Exercisable, Weighted-Average Remaining Contractual Term (in years)	5.2
Exercisable, Aggregate Intrinsic Value	$ 7,562
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested at the beginning of year (in shares)	270,793
Unvested at the beginning of year, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 68.07
Granted (in shares)	103,383									6,613	112,043
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 81.94	$ 73.51	$ 45.77
Vested (in shares)	(77,364)
Vested, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 68.51
Forfeited (in shares)	(13,975)
Forfeited, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 48.30
Unvested at the end of year (in shares)	282,837	270,793
Unvested at the end of year, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 74.00	$ 68.07