Consolidated Statement Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities:
Net income	$ 877	$ 834	$ 821
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,085	1,002	938
Amortization of nuclear fuel	68	79	95
Amortization of debt issuance costs and premium/discounts	22	19	20
Deferred income taxes and investment tax credits, net	148	167	224
Allowance for equity funds used during construction	(32)	(28)	(36)
Stock-based compensation costs	21	20	20
Other	22	(14)	44
Changes in assets and liabilities:
Receivables	(47)	79	(24)
Inventories	(25)	(10)	39
Accounts and wages payable	40	(3)	(22)
Taxes accrued	34	(8)	(10)
Regulatory assets and liabilities	(254)	164	201
Assets, other	(83)	(59)	2
Liabilities, other	(111)	(33)	(117)
Pension and other postretirement benefits	(38)	(39)	(25)
Net cash provided by operating activities	1,727	2,170	2,170
Cash Flows From Investing Activities:
Capital expenditures	(2,669)	(2,411)	(2,286)
Wind generation expenditures	(564)	0	0
Nuclear fuel expenditures	(66)	(31)	(52)
Purchases of securities – nuclear decommissioning trust fund	(224)	(256)	(315)
Proceeds from sales and maturities	183	260	299
Purchase of bonds	0	(207)	0
Proceeds from sale of remarketed bonds	0	207	0
Other	11	3	18
Net cash used in investing activities	(3,329)	(2,435)	(2,336)
Cash Flows From Financing Activities:
Dividends on common stock	(494)	(472)	(451)
Dividends paid to noncontrolling interest holders	(6)	(6)	(6)
Short-term debt, net	50	(157)	112
Maturities of long-term debt	(442)	(580)	(841)
Issuances of long-term debt	2,183	1,527	1,352
Issuances of common stock	476	68	74
Employee payroll taxes related to stock-based compensation	(20)	(29)	(19)
Debt issuance costs	(20)	(17)	(14)
Other	0	0	(2)
Net cash provided by financing activities	1,727	334	205
Net change in cash, cash equivalents, and restricted cash	125	69	39
Cash, cash equivalents, and restricted cash at beginning of year	176	107	68
Cash, cash equivalents, and restricted cash at end of year	301	176	107
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	383	367	387
Income taxes, net	13	13	21
Union Electric Company
Cash Flows From Operating Activities:
Net income	439	429	481
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	613	564	533
Amortization of nuclear fuel	68	79	95
Amortization of debt issuance costs and premium/discounts	6	5	6
Deferred income taxes and investment tax credits, net	17	(19)	(9)
Allowance for equity funds used during construction	(19)	(19)	(27)
Other	22	13	17
Changes in assets and liabilities:
Receivables	(8)	75	(32)
Inventories	(11)	(13)	30
Accounts and wages payable	26	16	(21)
Taxes accrued	9	(15)	(1)
Regulatory assets and liabilities	(166)	17	201
Assets, other	(2)	(28)	2
Liabilities, other	(80)	(32)	(13)
Pension and other postretirement benefits	(3)	(5)	(2)
Net cash provided by operating activities	911	1,067	1,260
Cash Flows From Investing Activities:
Capital expenditures	(1,102)	(1,076)	(914)
Wind generation expenditures	(564)	0	0
Nuclear fuel expenditures	(66)	(31)	(52)
Purchases of securities – nuclear decommissioning trust fund	(224)	(256)	(315)
Proceeds from sales and maturities	183	260	299
Purchase of bonds	0	(207)	0
Proceeds from sale of remarketed bonds	0	207	0
Money pool advances, net	(139)	0	0
Other	8	8	6
Net cash used in investing activities	(1,904)	(1,095)	(976)
Cash Flows From Financing Activities:
Dividends on common stock	(66)	(430)	(375)
Dividends on preferred stock	(3)	(3)	(3)
Short-term debt, net	(234)	179	16
Maturities of long-term debt	(92)	(580)	(384)
Issuances of long-term debt	1,012	778	423
Debt issuance costs	(9)	(9)	(5)
Capital contribution from parent	491	124	45
Net cash provided by financing activities	1,099	59	(283)
Net change in cash, cash equivalents, and restricted cash	106	31	1
Cash, cash equivalents, and restricted cash at beginning of year	39	8	7
Cash, cash equivalents, and restricted cash at end of year	145	39	8
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	190	190	196
Income taxes, net	25	101	128
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	382	346	307
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	434	405	375
Amortization of debt issuance costs and premium/discounts	12	12	13
Deferred income taxes and investment tax credits, net	118	80	88
Allowance for equity funds used during construction	(13)	(9)	(9)
Other	8	7	11
Changes in assets and liabilities:
Receivables	(28)	11	0
Inventories	(15)	2	8
Accounts and wages payable	15	(19)	(13)
Taxes accrued	(23)	21	(13)
Regulatory assets and liabilities	(72)	155	1
Assets, other	(76)	(23)	(1)
Liabilities, other	(46)	(5)	(92)
Pension and other postretirement benefits	(30)	(30)	(25)
Net cash provided by operating activities	679	962	659
Cash Flows From Investing Activities:
Capital expenditures	(1,447)	(1,208)	(1,258)
Other	3	3	10
Net cash used in investing activities	(1,444)	(1,205)	(1,248)
Cash Flows From Financing Activities:
Dividends on common stock	(9)	0	0
Dividends on preferred stock	(3)	(3)	(3)
Short-term debt, net	(53)	(19)	10
Money pool borrowings, net	19	0	0
Maturities of long-term debt	0	0	(457)
Issuances of long-term debt	373	299	929
Debt issuance costs	(4)	(4)	(9)
Capital contribution from parent	464	15	160
Other	0	0	(2)
Net cash provided by financing activities	787	288	628
Net change in cash, cash equivalents, and restricted cash	22	45	39
Cash, cash equivalents, and restricted cash at beginning of year	125	80	41
Cash, cash equivalents, and restricted cash at end of year	147	125	80
Cash Paid (Refunded) During the Year:
Interest (net of amounts capitalized, respectively)	137	127	144
Income taxes, net	$ 41	$ 4	$ 28