Fair Value Measurements (Fair Value Hierarchy Classification) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	$ 138	$ 204
Customer financing notes receivable	250	260
Short Term borrowings	2,314	126
Long-term debt (excluding capitalized leases)	22,530	22,254
Long-term liabilities	276	74
Portion at Other than Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	146	214
Customer financing notes receivable	252	262
Short Term borrowings	2,314	126
Long-term debt (excluding capitalized leases)	19,650	19,634
Long-term liabilities	289	80
UTC Climate, Controls & Security [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	126
Quoted price in active markets (Level 1) [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	0
Customer financing notes receivable	0
Short Term borrowings	0
Long-term debt (excluding capitalized leases)	0
Long-term liabilities	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	138
Customer financing notes receivable	250
Short Term borrowings	2,180
Long-term debt (excluding capitalized leases)	22,138
Long-term liabilities	276
Unobservable inputs (Level 3) [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term receivables	0
Customer financing notes receivable	0
Short Term borrowings	134
Long-term debt (excluding capitalized leases)	392
Long-term liabilities	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	982	961
Derivative Assets	131	142
Derivative Liabilities	610	319
Fair Value, Measurements, Recurring [Member] | Quoted price in active markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	982	961
Derivative Assets	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Derivative Assets	131	142
Derivative Liabilities	610	319
Fair Value, Measurements, Recurring [Member] | Unobservable inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Derivative Assets	0	0
Derivative Liabilities	0	0
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Dispositions		3
Fair Value, Measurements, Nonrecurring [Member] | Quoted price in active markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Dispositions		0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Dispositions		3
Fair Value, Measurements, Nonrecurring [Member] | Unobservable inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Dispositions		$ 0