Shareholders' Equity (Details) (USD $) Share data in Thousands, except Per Share data	1 Months Ended	6 Months Ended		6 Months Ended
	Feb. 28, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Common Stock [Member]	Jun. 30, 2010 Common Stock [Member]	Jun. 30, 2011 Paid-In Capital [Member]	Jun. 30, 2010 Paid-In Capital [Member]
Amount transferred from paid-in capital to common stock, stock split					$ (42,126,000)		$ 42,126,000
Common stock, par value		$ 2	$ 2
Common stock, authorized		200,000	200,000
Preferred stock, authorized		10,000	10,000
Preferred stock, issued		0	0
Share repurchase program, authorized amount	50,000,000
Stock repurchase program expiring date		February 2014
Stock repurchased and retired, shares		152		(152)
Stock repurchased and retired, value		(5,086,000)		(303,000)
Stock repurchase program, average price per share		$ 33.55
Stock repurchase program, remaining authorized repurchase amount		$ 44,900,000