Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Interest rate swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	37,586	24,212
Derivatives designated as hedging instruments
Derivative [Line Items]
Other Assets	0	650
Other Liabilities	451	718
Notional Amount	489,657	614,775
Derivatives designated as hedging instruments | Cash flow hedge | Interest rate swaps
Derivative [Line Items]
Other Assets	0	650
Other Liabilities	32	81
Notional Amount	482,000	607,000
Derivatives designated as hedging instruments | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Other Assets	0	0
Other Liabilities	419	637
Notional Amount	7,657	7,775
Derivatives not designated as hedging instruments
Derivative [Line Items]
Other Assets	30,132	25,767
Other Liabilities	37,451	23,612
Notional Amount	3,123,855	1,800,238
Derivatives not designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Other Assets	29,834	25,696
Other Liabilities	37,135	23,494
Notional Amount	2,996,861	1,687,005
Derivatives not designated as hedging instruments | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	298	71
Other Liabilities	316	118
Notional Amount	$ 126,994	$ 113,233