Insurance (Tables)

12 Months Ended

Dec. 31, 2017

Insurance [Abstract]

Schedule of Insurance Assets [Table Text Block]

Cash, cash equivalents, and marketable securities related to insurance activities at December 31 were as follows (in millions):

	2016		2017
Cash and cash equivalents	$	99	$	162
Marketable securities	475		449
Total cash, cash equivalents, and marketable securities	$	574	$	611

Schedule of Insurance Underwriting Losses and Expenses [Table Text Block]

The components of insurance expenses for the years ended December 31 were as follows (in millions):

	2015			2016			2017
Insurance losses	$	80		$	146		$	143
Loss adjustment expenses	5			5			8
Reinsurance income and other expenses, net	(16		)	(26		)	(27		)
Insurance expenses	$	69		$	125		$	124

Schedule of the Effect of Reinsurance Premiums Written and Earned [Table Text Block]

Insurance premiums written and earned for the years ended December 31 were as follows (in millions):

	2015						2016						2017
	Written			Earned			Written			Earned			Written			Earned
Direct	$	328		$	254		$	371		$	298		$	385		$	320
Assumed	—			—			—			—			—			—
Ceded	(194		)	(121		)	(215		)	(142		)	(227		)	(162		)
Net premiums	$	134		$	133		$	156		$	156		$	158		$	158