Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Variable Interest Entity [Line Items]
Expense related to qualified affordable housing projects	$ 1,600	$ 1,100	$ 3,300	$ 2,100
Remaining investment in qualified affordable housing projects	85,800		85,800		$ 84,900
Equity method investments	32,100		32,100		13,300
Remaining unfunded equity contributions	$ 73,400		73,400		$ 72,000
Investment tax credit		1,900	260	3,400
Impairment on tax credit projects		1,700	271	3,400
Other Noninterest Expense [Member]
Variable Interest Entity [Line Items]
Impairment on tax credit projects		$ 1,400	$ 214	$ 2,600