Shareholder's Equity (Narrative) (Details) (USD $)	0 Months Ended		3 Months Ended
	Apr. 24, 2012 M	Oct. 20, 2010 M	Mar. 31, 2012 Y	Mar. 31, 2011
Number of shares, options granted			0
Repurchase of common stock, shares			61,149	248,100
Repurchase of common stock			$ 1,560,000	$ 6,185,000
Average price per share			$ 25.49	$ 25
Shares repurchased to cover employee tax withholdings			48,139	22,802
Stock repurchased program authorized by the board of directors	40,000,000	40,000,000
Period of stock repurchase program, months	18	18
Portion of restricted stock vested outside directors			33.00%
Number of shares authorized for grant under share incentive plan			2,760,250
Unrecognized compensation cost on non vested awards			$ 11,169,000
Unrecognized compensation cost on non vested awards, weighted average period of recognition			1.3
Share based payment award shares purchased for award			75,624	1,508,706
Outside Directors [Member]
Number of installments in restricted stock granted to outside directors			3
Vesting period			2
Number of years restricted for trade			5
Employees [Member]
Additional options granted under stock incentive plan			0
Vesting period			4
Options term			10
Stock Options [Member]
Shares available for future grants/issuance under stock incentive plan			1,089,750
Restricted Stock [Member]
Shares available for future grants/issuance under stock incentive plan			331,575