Derivatives and Hedging - Credit and Market Risks (Details) - USD ($)		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivatives [Line Items]
Gain (loss) related to hedge, firm commitments no longer qualifying as a fair value hedge		$ 0	$ 0
Derivative assets		106,289,000		$ 93,409,000
Derivative, collateral, right to reclaim cash	[1]	80,045,000		92,396,000
Derivative, collateral, obligation to return	[1]	34,430,000		21,423,000
Other Assets
Derivatives [Line Items]
Derivative, collateral, right to reclaim cash		80,000,000		92,000,000
Deposits
Derivatives [Line Items]
Derivative, collateral, obligation to return		39,000,000		24,000,000
Free-standing derivatives not designated as hedging instrument
Derivatives [Line Items]
Derivative assets	[2]	163,688,000		188,370,000
Free-standing derivatives not designated as hedging instrument | Interest Rate Swap
Derivatives [Line Items]
Gain (loss) on derivative instruments held for trading purposes, net		0
Gain (loss) on derivative instruments held for non-trading purposes, net		0	$ 0
Free-standing derivatives not designated as hedging instrument | Total trading account assets and liabilities
Derivatives [Line Items]
Derivative assets	[2]	124,019,000		145,665,000
Derivatives designated as hedging instrument
Derivatives [Line Items]
Derivative assets	[2]	15,081,000		19,724,000
Derivatives designated as hedging instrument | Interest Rate Swap | Over the Counter
Derivatives [Line Items]
Credit risk derivatives, at fair value, net		15,000,000
Cash flow hedges | Derivatives designated as hedging instrument
Derivatives [Line Items]
Derivative assets	[2]	$ 234,000		$ 325,000

[1] The actual amount of collateral received/pledged is limited to the asset/liability balance and does not include excess collateral received/pledged. When excess collateral exists, the collateral shown in the table above has been allocated based on the percentage of the actual amount of collateral posted.

[2] Derivative assets, except for trading account assets that are recorded as a component of trading account assets on the Company's Unaudited Condensed Consolidated Balance Sheets, are recorded in other assets on the Company’s Unaudited Condensed Consolidated Balance Sheets.