Variable Interest Entities (Summary of the Impact of Qualifying LIHTC Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Low income housing tax credits
Variable Interest Entity [Line Items]
Amortization of qualifying LIHTC investments	$ 2,191	$ 2,362	$ 4,547	$ 4,640
Other tax benefits related to qualifying LIHTC investments	(2,560)	(2,598)	(5,097)	(4,998)
Other tax benefits related to qualifying LIHTC investments
Variable Interest Entity [Line Items]
Other tax benefits related to qualifying LIHTC investments	$ (894)	$ (910)	$ (1,584)	$ (1,829)