Schedule II, Valuation and Qualifying Accounts (Details) (Allowance for Bad Debts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Allowance for Bad Debts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1	$ 21,918		$ 24,698		$ 24,054
Charged to costs and expenses	16,784		16,323		20,371
Charged to other accounts	7,005	[1]	7,648	[1]	7,423	[1]
Deductions from reserves	23,202	[2]	26,751	[2]	27,150	[2]
Balance at Dec. 31	$ 22,505		$ 21,918		$ 24,698

[1] Recovery of amounts previously written off.

[2] Principally bad debts written off.