Derivative Instruments - Schedule of settlement of fair value hedges (Details) - Fair value hedges - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Notes Payable And Debt [Member]
Derivative [Line Items]
Cumulative reduction to interest expense	$ 0	$ 21,624
Remaining balance	$ 0	$ 0
Weighted average years remaining to maturity	0 years	0 years
Deposit liabilities
Derivative [Line Items]
Cumulative reduction to interest expense	$ 101,461	$ 93,042
Remaining balance	$ 131,734	$ 140,153
Weighted average years remaining to maturity	22 years	23 years 7 months 6 days