Shareholder's Equity (Narrative) (Details) (USD $)	0 Months Ended		6 Months Ended
	Apr. 24, 2012 M	Oct. 20, 2010 M	Jun. 30, 2012	Jun. 30, 2011
Number of shares, options granted			0	0
Repurchase of common stock, shares			216,994	248,100
Repurchase of common stock			$ 5,956,000	$ 6,185,000
Average price per share			$ 27.00	$ 25.00
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
Number of shares authorized for grant under share incentive plan			2,760,250
Unrecognized compensation cost on non vested awards			$ 9,543,000
Unrecognized compensation cost on non vested awards, weighted average period of recognition			1.2
Share based payment award shares purchased for award			39,062	792,165
Restricted Stock [Member]
Shares available for future grants/issuance under stock incentive plan			931,575
Stock Options [Member]
Vesting period			4
Options term			10
Shares available for future grants/issuance under stock incentive plan			1,069,084
Outside Directors [Member] | Restricted Stock [Member]
Vesting period			1	2
Employees [Member] | Restricted Stock [Member]
Number of installments in restricted stock granted			3
Vesting period			4