Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation and Qualifying Accounts (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Balance - beginning of period	$ 3,713		$ 3,942		$ 3,502
Charged to costs and expenses	2,455		2,430		2,256
Deductions	3,002	[1]	2,659	[1]	1,816	[1]
Balance - end of period	3,166		3,713		3,942
Accrued Risk Reserve [Member]
Balance - beginning of period	98,732		105,059		107,456
Charged to costs and expenses	67,900		60,202		60,640
Deductions	56,301		66,529		63,037
Balance - end of period	$ 110,331		$ 98,732		$ 105,059

[1] Amounts written off, net of recoveries