Retirement of Treasury Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Retirement of Treasury Stock [Abstract]
Retired shares of treasury stock (in shares)	1,141,400	1,409,832
Common Stock [Member]
Statement [Line Items]
Reductions due to retirement of treasury stock	1,141	1,410
Treasury Stock [Member]
Statement [Line Items]
Reductions due to retirement of treasury stock	42,905	33,086
Retained Earnings [Member]
Statement [Line Items]
Reductions due to retirement of treasury stock	18,845	7,411
Paid-in Capital [Member]
Statement [Line Items]
Reductions due to retirement of treasury stock	22,919	24,264