Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020
Cash flows from operating activities:
Net earnings (loss)	$ 11,840		$ (49,697)
Adjustments to reconcile net earnings to operating cash flows:
Investment (gains) losses	(5,211)		68,882
Depreciation and amortization	2,673		2,585
Other	(225)		(566)
Changes in operating assets and liabilities:
Losses and loss adjustment expenses	961		583
Deferred charges reinsurance assumed	252		260
Unearned premiums	2,390		2,006
Receivables and originated loans	(3,440)		(2,083)
Other assets	(397)		(1,140)
Other liabilities	(1,861)		17
Income taxes	2,324		(14,049)
Net cash flows from operating activities	9,306		6,798
Cash flows from investing activities:
Purchases of equity securities	(2,572)		(4,003)
Sales of equity securities	6,451		2,166
Purchases of U.S. Treasury Bills and fixed maturity securities	(32,313)		(31,551)
Sales of U.S. Treasury Bills and fixed maturity securities	4,090		5,328
Redemptions and maturities of U.S. Treasury Bills and fixed maturity securities	37,559		3,694
Purchases of loans and finance receivables	(11)		(595)
Collections of loans and finance receivables	109		70
Acquisitions of businesses, net of cash acquired	(47)		(26)
Purchases of property, plant and equipment and equipment held for lease	(2,519)		(2,968)
Other	449		81
Net cash flows from investing activities	11,196		(27,804)
Cash flows from financing activities:
Changes in short term borrowings, net	229		(1,133)
Acquisition of treasury stock	(6,580)		(1,741)
Other	(132)		(159)
Net cash flows from financing activities	(8,349)		(346)
Effects of foreign currency exchange rate changes	(61)		(184)
Increase (decrease) in cash and cash equivalents and restricted cash	12,092		(21,536)
Cash and cash equivalents and restricted cash at beginning of year*	48,396		64,632
Cash and cash equivalents and restricted cash at end of first quarter	60,488		43,096
Restricted cash, included in other assets at beginning of year	406		457
Restricted cash, included in other assets at end of first quarter	$ 434		$ 456
Restricted Cash and Cash Equivalents, Asset, Statement of Financial Position [Extensible List]	Other		Other
Insurance and Other [Member]
Cash flows from financing activities:
Proceeds from borrowings	$ 1,442		$ 1,613
Repayments of borrowings	(2,425)		(1,502)
Cash and cash equivalents at beginning of year	44,714	[1]	61,151
Cash and cash equivalents at end of first quarter	56,826	[1]	38,717
Railroad, Utilities and Energy [Member]
Cash flows from financing activities:
Proceeds from borrowings			4,324
Repayments of borrowings	(883)		(1,748)
Cash and cash equivalents at beginning of year	3,276	[1]	3,024
Cash and cash equivalents at end of first quarter	$ 3,228	[1]	$ 3,923

[1] Includes U.S. Treasury Bills with maturities of three months or less when purchased of $34.5 billion at March 31, 2021 and $23.2 billion at December 31, 2020.