Supplemental Information (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Allowance for Doubtful Accounts
Balance at beginning of period	$ 1,746	$ 1,922	$ 2,333
Additions	336		543
Recoveries/write-offs	(634)	(176)	(954)
Balance at end of period	$ 1,448	$ 1,746	$ 1,922