Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Weighted Average Shares:
Weighted average common stock outstanding for basic earnings per common share	1,074.0	1,100.3	1,082.1	1,100.6
Incremental common shares from assumed:
Incremental common shares from assumed exercise or issuance of stock-based awards	8.1	8.8	8.3	8.3
Weighted average common stock outstanding for diluted earnings per common share	1,082.1	1,109.1	1,090.4	1,108.9
Net Income (Loss):
Net income (loss)	$ 887	$ 114	$ 1,716	$ 2,317
Less: Net income (loss) attributable to noncontrolling interests	3	4	6	6
Less: Preferred stock dividends	46	46	52	52
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 838	$ 64	$ 1,658	$ 2,259
Basic	$ 0.78	$ 0.06	$ 1.53	$ 2.05
Diluted	$ 0.77	$ 0.06	$ 1.52	$ 2.04