Mortgage Loans on Real Estate (Troubled Debt Restructurings) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 loans	Dec. 31, 2012 loans
Financing Receivable, Modifications [Line Items]
Number of TDRs	17	24
Principal balance outstanding	$ 41,889	$ 68,050
Specific loan loss allowance	5,617	10,969
Net carrying amount	36,272	57,081
East [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	1	1
Principal balance outstanding	3,712	4,208
Specific loan loss allowance	949	1,425
Net carrying amount	2,763	2,783
Mountain [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	7	10
Principal balance outstanding	21,514	28,786
Specific loan loss allowance	631	1,702
Net carrying amount	20,883	27,084
South Atlantic [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	6	9
Principal balance outstanding	10,792	23,358
Specific loan loss allowance	3,314	5,047
Net carrying amount	7,478	18,311
East North Central [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	1	1
Principal balance outstanding	2,219	2,232
Specific loan loss allowance	467	467
Net carrying amount	1,752	1,765
West North Central [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	1	3
Principal balance outstanding	1,938	9,466
Specific loan loss allowance	0	2,328
Net carrying amount	1,938	7,138
West South Central [Member]
Financing Receivable, Modifications [Line Items]
Number of TDRs	1
Principal balance outstanding	1,714
Specific loan loss allowance	256
Net carrying amount	$ 1,458