Equity (Details 2) (USD $)		12 Months Ended				0 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2008	Dec. 31, 2013 Stock Options	Dec. 31, 2012 Stock Options	Dec. 31, 2013 Restricted stock	Dec. 31, 2012 Restricted stock	Jan. 31, 2014 Restricted stock Subsequent Event	Feb. 28, 2014 Restricted stock Subsequent Event	Jan. 31, 2014 Restricted stock Subsequent Event	Dec. 31, 2013 Restricted stock $ 46.54 per share grant price Vesting ratably over three-year period from the grant date	Dec. 31, 2013 Restricted stock $ 41.83 per share grant price Vesting ratably over three-year period from the grant date	Dec. 31, 2013 Restricted stock $ 36.26 per share grant price Vesting on June 1, 2016	Dec. 31, 2012 Restricted stock $ 31.77 per share grant price Vesting on June 15, 2015	Dec. 31, 2012 Restricted stock $ 31.77 per share grant price Vesting on January 10, 2016	Dec. 31, 2012 Restricted stock $ 31.77 per share grant price Vesting ratably over five-year period from the grant date	Dec. 31, 2012 Restricted stock $ 31.87 per share grant price Vesting ratably over three-year period from the grant date	Dec. 31, 2012 Restricted stock $ 34.90 per share grant price Vesting ratably over five-year period from the grant date	Dec. 31, 2012 Restricted stock $ 34.90 per share grant price Vesting on December 20, 2015
Stock Based Compensation Plans
Number of shares of common stock that have been reserved for awards (in shares)	600,000
Price per share									$ 46.54	$ 41.83	$ 36.26	$ 31.77	$ 31.77	$ 31.77	$ 31.87	$ 34.90	$ 34.90
Vesting period								3 years	3 years	3 years				5 years	3 years	5 years
Restricted stock activity
Outstanding at the beginning of the year (in shares)				195,449	165,134
Granted (in shares)				34,400	90,500	59,000	59,000		8,400	6,000	20,000	30,000	12,200	14,000	8,000	6,300	20,000
Vested (in shares)				(64,700)	(60,185)
Outstanding at the end of the year (in shares)				165,149	195,449
Compensation expense				$ 2,591,000	$ 1,809,000
Shares vested due to retirement of former SVP Marketing and Stratecig Planning				18,180
Granted (in dollars per share)						$ 36.81	$ 36.81
Compensation expense related to the accelerated vesting				457,000
Total compensation cost which will be recognized ratably over the remaining vesting period				3,818,000
Nonqualified stock option activity
Outstanding at the beginning of the year (in shares)		95,334	180,334
Exercised (in shares)		(22,000)	(85,000)
Outstanding at the end of the year (in shares)		73,334	95,334
Exercisable at the end of the period (in shares)		73,334	95,334
Weighted Average Price
Outstanding at the beginning of the year (in dollars per share)		$ 23.93	$ 23.33
Exercised (in dollars per share)		$ 23.79	$ 22.66
Outstanding at the end of the year (in dollars per share)		$ 23.97	$ 23.93
Exercisable at the end of the period (in dollars per share)		$ 23.97	$ 23.93
Aggregate intrinsic value of exercisable options at the end of the year		838,000
Weighted average remaining contractual life of options exercisable		3 years
Options Exercised (in shares)		22,000	85,000
Weighted Average Exercise Price (in dollars per share)		$ 23.79	$ 22.66
Option value		523,000	1,926,000
Market value		$ 865,000	$ 2,761,000
Weighted average exercise price of the options (in dollars per share)		$ 23.97	$ 23.93
Options scheduled to vest (in shares)		0