XML 145 R131.htm IDEA: XBRL DOCUMENT v3.3.1.900
Valuation and Qualifying Accounts (Detail) - Allowance for uncollectible Accounts - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at beginning of year $ 242,674 $ 237,143 $ 245,122
Amounts charged to income 437,100 381,337 298,711
Amounts written off 415,630 375,806 306,690
Balance at end of year $ 264,144 $ 242,674 $ 237,143