Schedule II-Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance For Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 5,647		$ 4,761		$ 4,086
"Additions" charged to costs and expenses	9,726		9,217		8,658
"Other" additions (deductions)	0		0		0
"Less" deductions	8,645		8,331		7,983
Balance at end of year	6,728		5,647		4,761
Insurance Reserves [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	30,548		28,067		23,722
"Additions" charged to costs and expenses	43,024	[1]	46,287	[1]	47,848	[1]
"Other" additions (deductions)	0		0		0
"Less" deductions	48,384	[2]	43,806	[2]	43,503	[2]
Balance at end of year	$ 25,188		$ 30,548		$ 28,067

[1] Includes costs and expenses incurred for premiums and claims related to health and general insurance.

[2] Includes costs and expenses paid for premiums and claims related to health and general insurance.