Consolidated Statement Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows From Operating Activities:
Net income	$ 995	$ 877	$ 834
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,219	1,085	1,002
Amortization of nuclear fuel	58	68	79
Amortization of debt issuance costs and premium/discounts	23	22	19
Deferred income taxes and investment tax credits, net	156	148	167
Allowance for equity funds used during construction	(43)	(32)	(28)
Stock-based compensation costs	22	21	20
Other	19	22	(14)
Changes in assets and liabilities:
Receivables	(74)	(47)	79
Inventories	(71)	(25)	(10)
Accounts and wages payable	28	40	(3)
Taxes accrued	1	34	(8)
Regulatory assets and liabilities	(439)	(254)	164
Assets, other	(126)	(83)	(59)
Liabilities, other	(74)	(111)	(33)
Pension and other postretirement benefits	(33)	(38)	(39)
Net cash provided by operating activities	1,661	1,727	2,170
Cash Flows From Investing Activities:
Capital expenditures	(2,954)	(2,669)	(2,411)
Wind generation expenditures	(525)	(564)	0
Nuclear fuel expenditures	(44)	(66)	(31)
Purchases of securities – nuclear decommissioning trust fund	(452)	(224)	(256)
Proceeds from sales and maturities	439	183	260
Purchase of bonds	0	0	(207)
Proceeds from sale of remarketed bonds	0	0	207
Other	8	11	3
Net cash used in investing activities	(3,528)	(3,329)	(2,435)
Cash Flows From Financing Activities:
Dividends on common stock	(565)	(494)	(472)
Dividends paid to noncontrolling interest holders	(5)	(6)	(6)
Short-term debt, net	55	50	(157)
Maturities of long-term debt	(8)	(442)	(580)
Issuances of long-term debt	1,997	2,183	1,527
Issuances of common stock	308	476	68
Redemptions of Ameren Illinois preferred stock	(13)	0	0
Employee payroll taxes related to stock-based compensation	(17)	(20)	(29)
Debt issuance costs	(18)	(20)	(17)
Other	(13)	0	0
Net cash provided by financing activities	1,721	1,727	334
Net change in cash, cash equivalents, and restricted cash	(146)	125	69
Cash, cash equivalents, and restricted cash at beginning of year	301	176	107
Cash, cash equivalents, and restricted cash at end of year	155	301	176
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	426	383	367
Income taxes, net	(1)	13	13
Union Electric Company
Cash Flows From Operating Activities:
Net income	521	439	429
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	704	613	564
Amortization of nuclear fuel	58	68	79
Amortization of debt issuance costs and premium/discounts	6	6	5
Deferred income taxes and investment tax credits, net	3	17	(19)
Allowance for equity funds used during construction	(26)	(19)	(19)
Other	19	22	13
Changes in assets and liabilities:
Receivables	(60)	(8)	75
Inventories	(32)	(11)	(13)
Accounts and wages payable	28	26	16
Taxes accrued	(27)	9	(15)
Regulatory assets and liabilities	(207)	(166)	17
Assets, other	(27)	(2)	(28)
Liabilities, other	(29)	(80)	(32)
Pension and other postretirement benefits	(2)	(3)	(5)
Net cash provided by operating activities	929	911	1,067
Cash Flows From Investing Activities:
Capital expenditures	(1,490)	(1,102)	(1,076)
Wind generation expenditures	(525)	(564)	0
Nuclear fuel expenditures	(44)	(66)	(31)
Purchases of securities – nuclear decommissioning trust fund	(452)	(224)	(256)
Proceeds from sales and maturities	439	183	260
Purchase of bonds	0	0	(207)
Proceeds from sale of remarketed bonds	0	0	207
Money pool advances, net	139
Money pool advances, net		(139)	0
Other	11	8	8
Net cash used in investing activities	(1,922)	(1,904)	(1,095)
Cash Flows From Financing Activities:
Dividends on common stock	(24)	(66)	(430)
Dividends on preferred stock	(3)	(3)	(3)
Short-term debt, net	165	(234)	179
Maturities of long-term debt	(8)	(92)	(580)
Issuances of long-term debt	524	1,012	778
Debt issuance costs	(5)	(9)	(9)
Capital contribution from parent	207	491	124
Net cash provided by financing activities	856	1,099	59
Net change in cash, cash equivalents, and restricted cash	(137)	106	31
Cash, cash equivalents, and restricted cash at beginning of year	145	39	8
Cash, cash equivalents, and restricted cash at end of year	8	145	39
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	205	190	190
Income taxes, net	19	25	101
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	427	382	346
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	471	434	405
Amortization of debt issuance costs and premium/discounts	13	12	12
Deferred income taxes and investment tax credits, net	165	118	80
Allowance for equity funds used during construction	(17)	(13)	(9)
Other	10	21	16
Changes in assets and liabilities:
Receivables	(17)	(28)	11
Inventories	(40)	(15)	2
Accounts and wages payable	2	15	(19)
Taxes accrued	22	(23)	21
Regulatory assets and liabilities	(222)	(72)	155
Assets, other	(75)	(76)	(23)
Liabilities, other	(45)	(46)	(5)
Pension and other postretirement benefits	(32)	(30)	(30)
Net cash provided by operating activities	662	679	962
Cash Flows From Investing Activities:
Capital expenditures	(1,432)	(1,447)	(1,208)
Other	(5)	3	3
Net cash used in investing activities	(1,437)	(1,444)	(1,205)
Cash Flows From Financing Activities:
Dividends on common stock	0	(9)	0
Dividends on preferred stock	(2)	(3)	(3)
Short-term debt, net	103	(53)	(19)
Money pool borrowings, net	(19)	19	0
Issuances of long-term debt	449	373	299
Redemption of preferred stock	(13)	0	0
Debt issuance costs	(6)	(4)	(4)
Capital contribution from parent	262	464	15
Other	(13)	0	0
Net cash provided by financing activities	761	787	288
Net change in cash, cash equivalents, and restricted cash	(14)	22	45
Cash, cash equivalents, and restricted cash at beginning of year	147	125	80
Cash, cash equivalents, and restricted cash at end of year	133	147	125
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	148	137	127
Income taxes, net	$ (41)	$ 41	$ 4