Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Held-to-maturity, fair value	$ 743	$ 850
Preferred stock, authorized shares	4,400,000	4,400,000
Common stock, authorized shares	350,000,000	350,000,000
Common stock, issued shares	199,712,000	203,085,000
Common stock, outstanding shares	199,712,000	203,085,000