Summary of Significant Accounting Policies Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Deferred Tax Liabilities, Net	$ 17,301				$ 13,940				$ 17,301	$ 13,940
Net income	(297)	2,911	403	1,512	1,798	2,053	3,009	1,622	4,529	8,482	14,704
Weighted Average Number of Shares Outstanding, Basic									50,007	49,811	49,689
Net Income Allocated to Class A Stock									4,483	8,397	14,546
Net Income Allocated to Class B Stock									$ 46	$ 85	$ 158
Common Class A [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic									49,005	48,809	48,687
Earnings Per Share, Basic and Diluted									$ 0.09	$ 0.17	$ 0.30
Common Class B [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic and Diluted									1,002	1,002	1,002
Earnings Per Share, Basic and Diluted									$ 0.05	$ 0.09	$ 0.15