Equity (Details 3) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Restricted stock activity
Granted (in shares)			92,150
Equity Participation Plan 2015 [Member]
Stock Based Compensation Plans
Number of shares of common stock that have been reserved for awards (in shares)	1,400,000		1,400,000
Options granted (in shares)			0
Equity Participation Plan 2008 [Member]
Restricted stock activity
Granted (in shares)				87,500
Equity Participation Plan 2008 [Member] | Grant Date Price 42.30 [Member] | Vesting Date 2 June 2016 [Member]
Restricted stock activity
Granted (in shares)			8,400
Price per share			$ 42.30
Employee Stock Option [Member]
Stock Based Compensation Plans
Vesting period				3 years
Option exercised (in shares)			3,333	11,666
Weighted Average Exercise Price (in dollars per share)			$ 23.79	$ 23.79
Value of options exercised	$ 79,000	$ 277,000	$ 79,000	$ 277,000
Market value of options on the date of exercise	$ 140,000	455,000	$ 140,000	455,000
Options outstanding at end of the period (in shares)	40,001		40,001
Options exercisable at end of the period (in shares)	30,001		30,001
Compensation expense related to the vesting of stock awards	$ 4,000	4,000	$ 8,000	$ 5,000
Remaining compensation expense to be recognized related to the future service period
Options scheduled to vest (in shares)	10,000		10,000
Remaining compensation expense	$ 25,000		$ 25,000
Employee Stock Option [Member] | Vesting Through December 31 2015 [Member]
Remaining compensation expense to be recognized related to the future service period
Remaining compensation expense	$ 7,000		$ 7,000
Employee Stock Option [Member] | Vesting Through December 31 2016 [Member]
Remaining compensation expense to be recognized related to the future service period
Options scheduled to vest (in shares)	5,000		5,000
Remaining compensation expense	$ 15,000		$ 15,000
Employee Stock Option [Member] | Vesting Through December 31 2017 [Member]
Remaining compensation expense to be recognized related to the future service period
Options scheduled to vest (in shares)	5,000		5,000
Remaining compensation expense	$ 3,000		$ 3,000
Employee Stock Option [Member] | Equity Participation Plan 2008 [Member]
Stock Based Compensation Plans
Options granted (in shares)				15,000
Options granted (in dollars per share)				$ 38.43
Restricted Stock [Member]
Stock Based Compensation Plans
Compensation expense related to the vesting of stock awards	$ 1,095,000	$ 779,000	$ 2,073,000	$ 1,444,000
Remaining compensation expense to be recognized related to the future service period
Restricted common stock scheduled to vest (in shares)	228,547		228,547
Remaining compensation expense	$ 6,140,000		$ 6,140,000
Restricted Stock [Member] | Vesting Through December 31 2015 [Member]
Remaining compensation expense to be recognized related to the future service period
Restricted common stock scheduled to vest (in shares)	41,200		41,200
Remaining compensation expense	$ 1,919,000		$ 1,919,000
Restricted Stock [Member] | Vesting Through December 31 2016 [Member]
Remaining compensation expense to be recognized related to the future service period
Restricted common stock scheduled to vest (in shares)	102,060		102,060
Remaining compensation expense	$ 2,618,000		$ 2,618,000
Restricted Stock [Member] | Vesting Through December 31 2017 [Member]
Remaining compensation expense to be recognized related to the future service period
Restricted common stock scheduled to vest (in shares)	57,367		57,367
Remaining compensation expense	$ 1,416,000		$ 1,416,000
Restricted Stock [Member] | Vesting Through December 31, 2018 [Member]
Remaining compensation expense to be recognized related to the future service period
Restricted common stock scheduled to vest (in shares)	27,920		27,920
Remaining compensation expense	$ 187,000		$ 187,000
Restricted Stock [Member] | Equity Participation Plan 2015 [Member]
Restricted stock activity
Granted (in shares)			0
Restricted Stock [Member] | Equity Participation Plan 2008 [Member]
Restricted stock activity
Number of shares cancelled (in shares)			640
Granted (in shares)				87,500
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 44.45 [Member] | Vesting over Three Year Period from Grant Date [Member]
Stock Based Compensation Plans
Vesting period			3 years
Restricted stock activity
Granted (in shares)			65,750
Price per share			$ 44.45
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 42.30 [Member] | Vesting over Three Year Period from Grant Date [Member]
Stock Based Compensation Plans
Vesting period			3 years
Restricted stock activity
Granted (in shares)			18,000
Price per share			$ 42.30
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 36.81 [Member] | Vesting over Three Year Period from Grant Date [Member]
Stock Based Compensation Plans
Vesting period				3 years
Restricted stock activity
Granted (in shares)				59,000
Price per share				$ 36.81
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 38.43 [Member] | Vesting over Three Year Period from Grant Date [Member]
Stock Based Compensation Plans
Vesting period				3 years
Restricted stock activity
Granted (in shares)				3,000
Price per share				$ 38.43
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 40.05[Member] | Vesting over Three Year Period from Grant Date [Member]
Stock Based Compensation Plans
Vesting period				3 years
Restricted stock activity
Granted (in shares)				15,000
Price per share				$ 40.05
Restricted Stock [Member] | Equity Participation Plan 2008 [Member] | Grant Date Price 40.05[Member] | Vesting Date 9 June2015 [Member]
Restricted stock activity
Granted (in shares)				10,500
Price per share				$ 40.05