CONSOLIDATED STATEMENT OF INCOME (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OTTI losses in the non-credit component of such impaired securities recognized in AOCI, net of tax	$ 0	$ 0	$ 0
Held-to-maturity Securities [Member]
Increase in credit losses for which an other-than-temporary impairment was previously recognized	0	0
Held-to-maturity Securities [Member] | Other Revenues [Member]
Increase in credit losses for which an other-than-temporary impairment was previously recognized	$ 0	$ 0	$ 11,000,000