Derivative Instruments - Schedule of settlement of fair value hedges (Details) (Fair value hedges, USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Notes payable and debt
Derivative [Line Items]
Cumulative reduction to interest expense	$ 20,810	$ 16,903
Remaining balance	814	4,721
Weighted average years remaining to maturity	0 years 2 months 12 days	1 year 2 months 12 days
Deposit liabilities
Derivative [Line Items]
Cumulative reduction to interest expense	90,615	29,257
Remaining balance	$ 142,580	$ 203,938
Weighted average years remaining to maturity	24 years 0 months 0 days	24 years 2 months 12 days