Investments (Net Unrealized Investment Gains Losses) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities	$ 4,858	$ 4,311
Fixed maturity securities with noncredit OTTI losses in AOCI	(31)	(34)	(45)
Total fixed maturity securities	4,827	4,277
Equity securities	77	69
Derivatives	376	282
Other	13	9
Subtotal	5,293	4,637
Future policy benefits	(712)	(503)
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	(1)	(2)
DAC, VOBA and DSI	(390)	(403)
Subtotal	(1,103)	(908)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	11	12
Deferred income tax benefit (expense)	(1,468)	(1,308)
Net unrealized investment gains (losses)	$ 2,733	$ 2,433