Financing Receivables - Mortgage Loan Portfolio as Collectively or Individually Evaluated for Impairment (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]      
Mortgage loans, carrying value $ 570,486 $ 629,256  
Mortgage loans, net
     
Financing Receivable, Allowance for Credit Losses [Line Items]      
Mortgage loans collectively evaluated for impairment 539,781 582,679  
Mortgage loans individually evaluated for impairment 33,030 49,828  
Allowance (2,325) (3,251) (3,346)
Mortgage loans, carrying value $ 570,486 $ 629,256