Derivative Financial Instruments - Notional Values (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Notional values	$ 9,500,000
Interest rate swaps
Derivatives, Fair Value [Line Items]
Notional values	9,485,485	$ 5,996,310
Interest rate swaps | Trading
Derivatives, Fair Value [Line Items]
Notional values	3,471,271	1,577,978
Interest rate swaps | Cash Flow Hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional values	1,183,176	1,280,367
Interest rate swaps | Fair Value Hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional values	$ 4,831,038	$ 3,137,965