Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Aggregate dividends declared during the period for each share of preferred stock outstanding.

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Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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Subsequent Events (Dividends - Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended													12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Estimated aggregate dividend payment														$ 1,678	$ 1,717	$ 1,736
Series A Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate		$ 0.253	$ 0.256	$ 0.256	$ 0.250	$ 0.253	$ 0.256	$ 0.256	$ 0.250	$ 0.253	$ 0.256	$ 0.256	$ 0.253	$ 1.015	$ 1.015	$ 1.018
Preferred stock, dividends		$ 6	$ 6	$ 7	$ 6	$ 6	$ 6	$ 7	$ 6	$ 6	$ 6	$ 7	$ 6	$ 25	$ 25	$ 25
Series D Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate		$ 0.000	$ 28.233	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 28.233	$ 0.000	$ 0.000
Preferred stock, dividends		$ 0	$ 14	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 14	$ 0	$ 0
Series E Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate		$ 351.563	$ 394.531	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 0.000	$ 746.094	$ 0.000	$ 0.000
Preferred stock, dividends		$ 11	$ 12	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 23	$ 0	$ 0
Common stock
Subsequent Event [Line Items]
Estimated aggregate dividend payment		$ 415	$ 419	$ 428	$ 416	$ 422	$ 427	$ 431	$ 437	$ 441	$ 441	$ 441	$ 413	$ 1,678	$ 1,717	$ 1,736
Subsequent Event [Member]
Subsequent Event [Line Items]
Estimated aggregate dividend payment	$ 404
Subsequent Event [Member] \| Dividends Declared [Member] \| Series A Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate	$ 0.250
Preferred stock, dividends	$ 6
Subsequent Event [Member] \| Dividends Declared [Member] \| Series D Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate	$ 29.375
Preferred stock, dividends	$ 15
Subsequent Event [Member] \| Dividends Declared [Member] \| Series E Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock, dividend rate	$ 351.563
Preferred stock, dividends	$ 11
Subsequent Event [Member] \| Dividends Declared [Member] \| Common stock
Subsequent Event [Line Items]
Approved annual dividend, amount per share	$ 0.420