Schedule of Changes in SARs (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Share Based Grants Weighted Average Remaining Ter			9 years 6 months	9 years 8 months 13 days
Share Based Compensation Exercisable Contractual Term	8 years	2 years 1 month 7 days	8 years	2 years 1 month 7 days
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award			The SARs vest ratably over a three-year period and may be exercised at any point after vesting through 10 years from the date of issuance. Pursuant to the terms of the awards, upon exercise, the executive officers will receive, in shares of common stock, the excess of the market price of the award on the date of exercise over the market price of the award on the date of issuance.
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding beginning of the year, January 1 (shares)			50,471	57,282
SARs awarded (shares)			68,361	31,552
Outstanding at June 30, (shares)	118,832	88,834	118,832	88,834
SARs, Vested and Expected to Vest, Outstanding, shares	112,285	84,851	112,285	84,851
SARs, Exercisable, shares	27,458	48,999	27,458	48,999
SARs, Outstanding, Weighted Average Exercise Price	$ 30.80	$ 31.37	$ 30.80	$ 31.37	$ 31.61	$ 24.44
Awards, Weighted Average Exercise Price			$ 30.19	$ 43.95
Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 30.76	$ 31.27	$ 30.76	$ 31.27
Exercisable, Weighted Average Exercise Price	$ 28.84	$ 29.61	$ 28.84	$ 29.61
Shared Based Compensation Remaining Contractual Period	8 years 10 months 24 days	5 years 3 months 18 days	8 years 10 months 24 days	5 years 3 months 18 days	8 years 7 months 6 days	9 years 3 months 18 days
Vested and expected to vest, remaining contractual term	8 years 10 months 24 days	5 years	8 years 10 months 24 days	5 years
SARs, Outstanding, Intrinsic Value	$ 3,000	$ 313,000	$ 3,000	$ 313,000	$ 341,000	$ 1,020,000
Shared Based Awards Intrinsic Value			0	0
SARs, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	3,000	302,000	3,000	302,000
SARs, Exercisable, Aggregate Intrinsic Value	2,000	197,000	2,000	197,000
Total compensation cost related to SARs granted and not yet recognized (dollars)	$ 1,300,000		$ 1,300,000
Weighted average period expected to recognize SARs compensation costs not yet recognized (years)	2 years 2 months 28 days
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Terms of Separation Agreement with Former Executive		Pursuant to a separation agreement with our former chief executive officer and the original terms of the award, during the three and six months ended 2011, the vesting of 29,906 SARs was accelerated resulting in the acceleration of $0.6 million in stock-based compensation expense.