Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Equity Method Investments and Joint Ventures [Abstract]
Expense related to qualified affordable housing projects	$ 800,000	$ 400,000	$ 2,300,000	$ 1,600,000
Remaining investment in qualified affordable housing projects	42,900,000		42,900,000		$ 29,500,000
Equity method investments	19,500,000		19,500,000		10,900,000
Remaining unfunded equity contributions	36,500,000		36,500,000		16,000,000
Impairment on tax credit projects	$ 3,100,000		$ 3,100,000		$ 0