Components of General Tax Expense from Continuing Operations (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
General Tax Expense [Line Items]      
General taxes $ 234,642 $ 221,212 $ 210,478
Gross receipts and franchise
     
General Tax Expense [Line Items]      
General taxes 96,044 92,612 90,674
Property and capital stock
     
General Tax Expense [Line Items]      
General taxes 94,448 84,513 77,330
Payroll
     
General Tax Expense [Line Items]      
General taxes 31,375 32,724 31,705
Other general
     
General Tax Expense [Line Items]      
General taxes $ 12,775 $ 11,363 $ 10,769