Schedule II (Details) (Provision for Uncollectible Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Provision for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 5,337		$ 8,071		$ 6,268
Charged to Costs and Expenses	4,932		2,272		4,943
Charged to Other Accounts	110	[1]	562	[1]	(217)	[1]
Deductions	4,455	[2]	5,568	[2]	2,923	[2]
Ending Balance	$ 5,924		$ 5,337		$ 8,071

[1] Recoveries of accounts previously written off and minor adjustments.

[2] Uncollectible accounts written off.