Derivative Instruments (Details) - Schedule of settlement of fair value hedges (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Weighted average years to maturity	16 years 1 month 6 days
Notes Payable And Debt [Member] | Fair Value Hedging Member
Derivative [Line Items]
Cumulative reduction to interest expense	$ 14,949	$ 10,915
Fair Value Hedge Remaining Balance	6,675	10,709
Weighted average years to maturity	1 year 8 months 12 days	2 years 6 months
Deposit Liabilities [Member] | Fair Value Hedging Member
Derivative [Line Items]
Cumulative reduction to interest expense	21,395	9,376
Fair Value Hedge Remaining Balance	$ 211,800	$ 140,109
Weighted average years to maturity	25 years 3 months 18 days	30 years 8 months 12 days