Variable Interest Entities - Summary of the Impact of Qualifying LIHTC Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Low income housing tax credits
Variable Interest Entity [Line Items]
Amortization of qualifying LIHTC investments	$ 1,547	$ 3,774	$ 6,094	$ 8,414
Other tax benefits related to qualifying LIHTC investments	(2,584)	(3,103)	(7,681)	(8,101)
Other tax benefits related to qualifying LIHTC investments
Variable Interest Entity [Line Items]
Other tax benefits related to qualifying LIHTC investments	$ (1,412)	$ (2,478)	$ (2,996)	$ (4,307)