Minimum Capital Requirements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2017
Banking And Thrift [Abstract]
Capital conservative buffer percentage	2.50%
Description of capital adequacy purposes	Beginning in 2016, an additional conservation buffer was added to the minimum requirements for capital adequacy purposes, subject to a three year phase-in period. The capital conservative buffer will be fully phased in January 1, 2019 at 2.5 percent.