Share-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended									0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Jan. 02, 2013 Stock Award [Member]	Feb. 07, 2013 Stock Award [Member] Restricted Stock [Member]	Feb. 07, 2013 Restricted Stock [Member]
Share-based Compensation, Allocation and Classification in Financial Statements [Abstract]
Share-based compensation incurred	$ 10,371	$ 8,247	$ 6,487	$ 9,846	$ 7,308	$ 5,232	$ 525	$ 939	$ 1,255
Capitalized share-based compensation	(908)	(663)	(745)
Share-based compensation expense	9,463	7,584	5,742
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Volatility			30.00%
Expected dividend yield			4.00%
Expected term (in years)			4 years 4 months
Risk free interest rate			1.90%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of year (in shares)	517,653
Outstanding at the beginning of year, Weighted-Average Exercise Price (in dollars per share)	$ 61.08
Granted (in shares)	0	0
Granted, Weighted-Average Exercise Price (in dollars per share)	$ 0.00
Exercised (in shares)	(97,430)
Exercised, Weighted-Average Exercise Price (in dollars per share)	$ 58.46
Forfeited or expired (in shares)	(29,334)
Forfeited or Expired, Weighted-Average Exercise Price (in dollars per share)	$ 44.61
Outstanding at the end of year (in shares)	390,889	517,653
Outstanding at the end of year, Weighted-Average Exercise Price (in dollars per share)	$ 62.96	$ 61.08
Outstanding at the end of year, Intrinsic Value	16,048
Exercisable at the end of year (in shares)	293,946
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 65.66
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 2 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	5 years
Exercisable, Aggregate Intrinsic Value	$ 11,276
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested at the beginning of year (in shares)	282,837
Unvested at the beginning of year, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 74.00
Granted (in shares)	126,169									5,767	98,913
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period												3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 96.35	$ 81.94	$ 73.51
Vested (in shares)	(106,804)
Vested, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 72.78
Forfeited (in shares)	(14,522)
Forfeited, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 53.76
Unvested at the end of year (in shares)	287,680	282,837
Unvested at the end of year, Weighted-Average Grant-Date Fair Value (in dollars per share)	$ 85.28	$ 74.00