Stock-Based Compensation Plans (Details 3) $ / shares in Units, $ in Thousands		12 Months Ended
	Jan. 01, 2014 item	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2012 shares	Oct. 31, 1996 shares
Additional disclosures
Stock-based compensation expense | $		$ 14,703	$ 13,314	$ 17,775
Capitalized stock-based compensation cost | $		$ 9,667	5,457	8,379
Forfeiture rate (as a percent)		1.00%
Employee Stock Purchase Plan [Abstract]
Shares issued under Employee Stock Purchase Plan		10,667
Stock-based compensation expense | $		$ 14,703	$ 13,314	$ 17,775
Stock Options
Weighted average assumptions
Weighted average fair value per share (in dollars per share) | $ / shares				$ 26.78
Life of options (in years)				5 years
Dividend yield (as a percent)				3.70%
Volatility (as a percent)				34.00%
Risk-free interest rate (as a percent)				0.91%
Additional disclosures
Unrecognized compensation cost for unvested stock options | $		$ 99
Weighted average period for recognition of unrecognized compensation cost		1 month 6 days
Forfeiture rate (as a percent)		1.00%
Restricted stock
Additional disclosures
Granted (in shares)		61,953	98,954	123,977
Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Issued in Period Fair Value | $		$ 10,720	$ 12,799
Outstanding unvested shares granted		147,884	179,307	182,083	202,218
Number of shares vested during period related to new awards		91,847	93,963	141,673
Grant date fair value per share (in dollars per share) | $ / shares		$ 173.04	$ 129.35	$ 129.21
Unrecognized compensation cost for unvested stock options | $		$ 21,096
Weighted average period for recognition of unrecognized compensation cost		3 years 7 months 6 days
Performance awards
Weighted average assumptions
Dividend yield (as a percent)		3.00%	3.60%	3.30%
Maximum Measurement Period (in years)		3 years
Award vesting period (in years)		3 years
Additional disclosures
Granted (in shares)		85,636	136,276	191,008
Baseline share value (in dollars per share) | $ / shares		$ 166.23	$ 128.97	$ 130.23
Estimated volatility, minimum (as a percent)		12.00%	17.60%	17.00%
Estimated volatility, maximum (as a percent)		17.30%	18.60%	21.00%
Risk-free interest rate, minimum (as a percent)		0.07%	0.04%	0.09%
Risk-free interest rate, maximum (as a percent)		1.09%	0.72%	0.46%
Average estimated fair value (in dollars per share) | $ / shares		$ 139.18	$ 103.20	$ 70.00
Outstanding unvested shares granted		238,266	239,902	189,765	0
Grant date fair value per share (in dollars per share) | $ / shares		$ 148.49	$ 117.43	$ 70.00
Performance awards | Maximum
Weighted average assumptions
Percentage of stock based compensation elected to be received in the form of stock options upon the election of the recipient		25.00%
Non Qualified Employee Stock Purchase Plan [Member]
Additional disclosures
Stock-based compensation expense | $		$ 321	$ 407	$ 174
Employee Stock Purchase Plan [Abstract]
Employee stock purchase plan, shares of common stock reserved for issuance						1,000,000
Employee stock purchase plan, remaining shares of common stock available for issuance		704,160
Employment period of full-time employees for becoming eligible to participate in the plan (in months)		1 month
Employment period of other employees for becoming eligible to participate in the plan (in months)		12 months
Purchase period (in months)			7 months
Number of purchase periods | item	2
Employee stock purchase plan, discounted stock price percentage		85.00%
Shares issued under Employee Stock Purchase Plan		10,667	9,848	9,260
Stock-based compensation expense | $		$ 321	$ 407	$ 174