Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified				12 Months Ended		24 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 2011 Common Stock Repurchase Program [Member]	Dec. 31, 2011 2011 Common Stock Repurchase Program [Member]	Dec. 31, 2012 2011 Common Stock Repurchase Program [Member]	Sep. 30, 2012 2011 Common Stock Repurchase Program [Member]	Sep. 30, 2011 2011 Common Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, shares of common stock approved for repurchase							500,000	500,000
Stock repurchase program, percentage of shares of common stock approved for repurchase								6.50%
Stock repurchase program, expiration date							Oct. 01, 2013	Sep. 30, 2012
Stock repurchased during period, shares				65,580	13,244	78,824
Shares repurchased, average cost per share				$ 31.98	$ 29.34
The percentage of the stock repurchase program's allottment repurchased during the period						16.00%
The percentage of outstanding shares repurchased during the period						1.00%
Dividends declared to shareholders	$ 7,700	$ 11,500	$ 7,700