Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts	$ 2,548	$ 2,716
Amounts pledged	$ 653,651	$ 102,501
Class A non-voting common stock
Common stock, shares issued	13,572,265	13,268,522
Common stock, shares outstanding	13,572,265	13,268,522
Class B voting common stock
Common stock, shares issued	99,680	99,680
Common stock, shares outstanding	99,680	99,680