Medical Costs Payable (Tables)

12 Months Ended

Dec. 31, 2017

Insurance [Abstract]

Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]

The following table shows the components of the change in medical costs payable for the years ended December 31:

(in millions)	2017			2016			2015
Medical costs payable, beginning of period	$	16,391		$	14,330		$	12,040
Acquisitions	83			—			—
Reported medical costs:
Current year	130,726			117,258			104,195
Prior years	(690		)	(220		)	(320		)
Total reported medical costs	130,036			117,038			103,875
Medical payments:
Payments for current year	(113,811		)	(101,696		)	(90,630		)
Payments for prior years	(14,828		)	(13,281		)	(10,955		)
Total medical payments	(128,639		)	(114,977		)	(101,585		)
Medical costs payable, end of period	$	17,871		$	16,391		$	14,330

Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]

The following is information about incurred and paid medical cost development as of December 31, 2017:

	Net Incurred Medical Costs
(in millions)	For the Years ended December 31,
Year	2016			2017
2016	$	117,258		$	116,622
2017				130,726
Total				$	247,348
	Net Cumulative Medical Payments
(in millions)	For the Years ended December 31,
Year	2016			2017
2016	$	(101,696	)	$	(116,187	)
2017				(113,811		)
Total				(229,998		)
Net remaining outstanding liabilities prior to 2016				521
Total medical costs payable				$	17,871