Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 2,307	$ 1,981
Common units issued (in shares)	27,711,201	31,129,065
Common units outstanding (in shares)	27,711,201	31,129,065
Common units held in treasury (in shares)	8,800,330	5,373,241
Common units held in treasury, at cost	$ 135,694	$ 78,977