Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Interest rate swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	44,649	24,212
Derivatives designated as hedging instruments
Derivative [Line Items]
Other Assets	0	650
Other Liabilities	389	718
Notional Amount	489,597	614,775
Derivatives designated as hedging instruments | Cash flow hedge interest rate swaps and caps | Interest rate swaps
Derivative [Line Items]
Other Assets	0	650
Other Liabilities	44	81
Notional Amount	482,000	607,000
Derivatives designated as hedging instruments | Fair value hedge interest rate swaps | Interest rate swaps
Derivative [Line Items]
Other Assets	0	0
Other Liabilities	345	637
Notional Amount	7,597	7,775
Derivatives not designated as hedging instruments
Derivative [Line Items]
Other Assets	28,539	25,767
Other Liabilities	44,528	23,612
Notional Amount	3,370,877	1,800,238
Derivatives not designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Other Assets	28,205	25,696
Other Liabilities	44,260	23,494
Notional Amount	3,252,701	1,687,005
Derivatives not designated as hedging instruments | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	334	71
Other Liabilities	268	118
Notional Amount	$ 118,176	$ 113,233