MBS Investments Terms of MBS (Details) (Trust Portfolio--MBS Bonds [Member], USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Jun. 30, 2014	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available for Sale Securities, not Including Premiums	$ 14,765,000		$ 42,830,000		$ 3,700,000	$ 31,620,000
Debt, Weighted Average Interest Rate	1.10%		1.30%
Standard & Poor's, AAA Rating [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Instrument, Credit Rating	"AAA"	[1]	“AAA”	[1]
Available for Sale Securities, not Including Premiums	5,000,000		22,710,000
Debt Instrument, Maturity Date	Jul. 01, 2032		Dec. 09, 2037
Debt, Weighted Average Interest Rate	4.60%		4.05%
Standard & Poor's, AA Rating [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Instrument, Credit Rating	"AA"	[1]	“AA”	[1]
Available for Sale Securities, not Including Premiums	$ 9,765,000		$ 20,120,000
Debt Instrument, Maturity Date	Jul. 09, 2036		Feb. 05, 2037
Debt, Weighted Average Interest Rate	4.20%		4.00%

[1] (1) MBS are reported based on the lowest rating issued by a Rating Agency, if more than one rating is issued on the security, at the date presented.