Fair Value (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

The following table presents a summary of fair value measurements by level and carrying values for items measured at fair value on a recurring basis in the Condensed Consolidated Balance Sheets:

(in millions)	Quoted Prices in Active Markets (Level 1)			Other Observable Inputs (Level 2)			Unobservable Inputs (Level 3)			Total Fair and Carrying Value
March 31, 2018
Cash and cash equivalents	$	16,249		$	1,994		$	—		$	18,243
Debt securities - available-for-sale:
U.S. government and agency obligations	2,631			255			—			2,886
State and municipal obligations	—			7,139			—			7,139
Corporate obligations	50			14,068			141			14,259
U.S. agency mortgage-backed securities	—			4,316			—			4,316
Non-U.S. agency mortgage-backed securities	—			1,142			—			1,142
Total debt securities - available-for-sale	2,681			26,920			141			29,742
Equity securities	1,791			13			143			1,947
Assets under management	950			1,972			—			2,922
Total assets at fair value	$	21,671		$	30,899		$	284		$	52,854
Percentage of total assets at fair value	41		%	58		%	1		%	100		%
December 31, 2017
Cash and cash equivalents	$	11,718		$	263		$	—		$	11,981
Debt securities - available-for-sale:
U.S. government and agency obligations	2,428			216			—			2,644
State and municipal obligations	—			7,660			—			7,660
Corporate obligations	65			12,989			140			13,194
U.S. agency mortgage-backed securities	—			3,911			—			3,911
Non-U.S. agency mortgage-backed securities	—			1,015			—			1,015
Total debt securities - available-for-sale	2,493			25,791			140			28,424
Equity securities	1,784			14			194			1,992
Assets under management	1,117			1,984			—			3,101
Total assets at fair value	$	17,112		$	28,052		$	334		$	45,498
Percentage of total assets at fair value	38		%	61		%	1		%	100		%

Fair Value Measurements, Nonrecurring [Table Text Block]

The following table presents a summary of fair value measurements by level and carrying values for certain financial instruments not measured at fair value on a recurring basis in the Condensed Consolidated Balance Sheets:

(in millions)	Quoted Prices in Active Markets (Level 1)		Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)		Total Fair Value		Total Carrying Value
March 31, 2018
Debt securities - held-to-maturity	$	260	$	66	$	264	$	590	$	591
Long-term debt and other financing obligations	$	—	$	32,892	$	—	$	32,892	$	31,162
December 31, 2017
Debt securities - held-to-maturity	$	267	$	4	$	265	$	536	$	536
Long-term debt and other financing obligations	$	—	$	34,504	$	—	$	34,504	$	31,542