Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statement of Comprehensive Income
Net income	$ 866	$ 928	$ 812	$ 833	$ 1,038	$ 919	$ 683	$ 1,052	$ 3,439	$ 3,692	$ 3,673
Other comprehensive income (loss):
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income									(1,020)	976	(2,734)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income									(14)	2	3
Net changes in benefit plan assets and obligations									66	(494)	647
Net changes in unrealized foreign currency translation									(461)	(289)	(112)
Other comprehensive income (loss) before income taxes									(1,429)	195	(2,196)
Income tax expense (benefit)									(392)	125	(770)
Other comprehensive income (loss), net of taxes									(1,037)	70	(1,426)
Comprehensive income									$ 2,402	$ 3,762	$ 2,247