Derivative Instruments - Schedule of settlement of fair value hedges (Details) (Fair value hedges, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Notes payable and debt
Derivative [Line Items]
Cumulative reduction to interest expense	$ 19,833	$ 15,926
Remaining balance	1,791	5,698
Weighted average years remaining to maturity	0 years 6 months 0 days	1 year 6 months
Deposit liabilities
Derivative [Line Items]
Cumulative reduction to interest expense	41,270	25,588
Remaining balance	$ 191,925	$ 207,607
Weighted average years remaining to maturity	22 years 2 months 12 days	24 years 8 months 12 days