Stockholders' Equity 2 (Details) - Current Stock Repurchase Program - USD ($) shares in Millions, $ in Millions	6 Months Ended
Sep. 30, 2018	Nov. 13, 2015
Stock repurchases
Stock repurchase program, Authorized amount		$ 750
Shares of common stock repurchased	2.3
Value of common stock repurchased	$ 80
Stock repurchase program, Remaining authorized common stock repurchase amount	$ 407

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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