Slicers (applies to each fact value in each table cell)

Reporting Entity [Axis]

0001002910 (http://www.sec.gov/CIK)

Income Tax Disclosure [Abstract]	Period [Axis]
	2016-01-01 - 2016-12-31
Income Tax Disclosure [Abstract]
Schedule Of Effective Income Tax Rate Reconciliation	The following table presents the principal reasons for the difference between the effective income tax rate and the statutory federal income tax rate for the years ended December 31, 2016, 2015, and 2014:   Ameren Missouri   Ameren Illinois   Ameren 2016           Statutory federal income tax rate: 35  %   35  %   35  % Increases (decreases) from:           Depreciation differences 1   —   — Amortization of deferred investment tax credit (1 )   —   — State tax 3   5   4 Stock-based compensation(a) —   —   (2 ) Valuation allowance —   —   1 Other permanent items —   (2 )   (1 ) Effective income tax rate 38  %   38  %   37  % 2015           Statutory federal income tax rate: 35  %   35  %   35  % Increases (decreases) from:           Depreciation differences —   (2 )   (1 ) Amortization of deferred investment tax credit (1 )   —   (1 ) State tax 3   5   5 Other permanent items —   (1 )   — Effective income tax rate 37  %   37  %   38  % 2014           Statutory federal income tax rate: 35  %   35  %   35  % Increases (decreases) from:           Amortization of deferred investment tax credit (1 )   —   (1 ) State tax 3   6   4 Other permanent items —   —   1 Effective income tax rate 37  %   41  %   39  % (a) Reflects the adoption of new authoritative accounting guidance related to share-based compensation. See Note 1 – Summary of Significant Accounting Policies for more information.
Schedule Of Components Of Income Tax Expense (Benefit)	The following table presents the components of income tax expense (benefit) for the years ended December 31, 2016, 2015, and 2014:   Ameren Missouri   Ameren Illinois   Other   Ameren 2016               Current taxes:               Federal $ 31   $ (8 )   $ (24 )   $ (1 ) State 6   12   (21 )   (3 ) Deferred taxes:               Federal 161   117   21   299 State 23   37   32   92 Amortization of deferred investment tax credits (5 )   —   —   (5 ) Total income tax expense $ 216   $ 158   $ 8   $ 382 2015               Current taxes:               Federal $ 110   $ (83 )   $ (29 )   $ (2 ) State 17   (11 )   (10 )   (4 ) Deferred taxes:               Federal 71   193   35   299 State 16   29   31   76 Amortization of deferred investment tax credits (5 )   (1 )   —   (6 ) Total income tax expense $ 209   $ 127   $ 27   $ 363 2014               Current taxes:               Federal $ (13 )   $ (51 )   $ 27   $ (37 ) State (3 )   (2 )   (32 )   (37 ) Deferred taxes:               Federal 222   159   (12 )   369 State 28   38   22   88 Amortization of deferred investment tax credits (5 )   (1 )   —   (6 ) Total income tax expense (benefit) $ 229   $ 143   $ 5   $ 377
Schedule Of Deferred Tax Assets And Liabilities Resulting From Temporary Differences	The following table presents the deferred tax assets and deferred tax liabilities recorded as a result of temporary differences at December 31, 2016 and 2015:   Ameren Missouri   Ameren Illinois   Other   Ameren 2016               Accumulated deferred income taxes, net liability (asset):               Plant related $ 3,103   $ 1,769   $ 147   $ 5,019 Regulatory assets, net 75   (1 )   —   74 Deferred employee benefit costs (76 )   (38 )   (97 )   (211 ) Revenue requirement reconciliation adjustments —   34   —   34 Tax carryforwards (66 )   (138 )   (472 )   (676 ) Other (23 )   5   42   24 Total net accumulated deferred income tax liabilities (assets) $ 3,013   $ 1,631   $ (380 )   $ 4,264 2015               Accumulated deferred income taxes, net liability (asset):               Plant related $ 2,931   $ 1,587   $ 37   $ 4,555 Regulatory assets, net 81   (1 )   —   80 Deferred employee benefit costs (76 )   (40 )   (91 )   (207 ) Revenue requirement reconciliation adjustments —   66   —   66 Tax carryforwards (65 )   (133 )   (405 )   (603 ) Other (27 )   1   20   (6 ) Total net accumulated deferred income tax liabilities (assets) $ 2,844   $ 1,480   $ (439 )   $ 3,885
Schedule Of Net Operating Loss Carryforwards And Tax Credit Carryforwards	The following table presents the components of deferred tax assets relating to net operating loss carryforwards, tax credit carryforwards, and charitable contribution carryforwards at December 31, 2016 and 2015:   Ameren Missouri   Ameren Illinois   Other   Ameren 2016               Net operating loss carryforwards:               Federal(a) $ 33   $ 137   $ 324   $ 494 State(a) 4   —   41   45 Total net operating loss carryforwards $ 37   $ 137   $ 365   $ 539 Tax credit carryforwards:               Federal(a) $ 29   $ 1   $ 79   $ 109 State(b) —   —   21   21 Total tax credit carryforwards $ 29   $ 1   $ 100   $ 130 Charitable contribution carryforwards(b) $ —   $ —   $ 18   $ 18 Valuation allowance(c) —   —   (11 )   (11 ) Total charitable contribution carryforwards $ —   $ —   $ 7   $ 7 2015               Net operating loss carryforwards:               Federal $ 35   $ 127   $ 245   $ 407 State 4   4   38   46 Total net operating loss carryforwards $ 39   $ 131   $ 283   $ 453 Tax credit carryforwards:               Federal $ 26   $ 1   $ 78   $ 105 State —   1   40   41 State valuation allowance —   —   (2 )   (2 ) Total tax credit carryforwards $ 26   $ 2   $ 116   $ 144 Charitable contribution carryforwards $ —   $ —   $ 10   $ 10 Valuation allowance —   —   (4 )   (4 ) Total charitable contribution carryforwards $ —   $ —   $ 6   $ 6 (a) Will expire between 2029 and 2036. (b) Will expire between 2017 and 2021. (c) See Schedule II under Part IV, Item 15, in this report for information on changes in the valuation allowance.