Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets:
Total	$ 2,349	$ 1,226
Other liabilities:
Total	5,146	1,689
Fixed income securities
Assets:
Debt securities, available-for-sale	444	442
Interest rate swaps
Assets:
Derivative asset	1,874	568
Other liabilities:
Derivative liabilities	344	173
Cross currency swaps
Assets:
Derivative asset		211
Other liabilities:
Derivative liabilities	3,651	912
Foreign exchange forwards
Assets:
Derivative asset	31	5
Forward starting interest rate swaps
Other liabilities:
Derivative liabilities	1,151	604
Level 1
Assets:
Total	0	0
Other liabilities:
Total	0	0
Level 1 | Fixed income securities
Assets:
Debt securities, available-for-sale	0	0
Level 1 | Interest rate swaps
Assets:
Derivative asset	0	0
Other liabilities:
Derivative liabilities	0	0
Level 1 | Cross currency swaps
Assets:
Derivative asset		0
Other liabilities:
Derivative liabilities	0	0
Level 1 | Foreign exchange forwards
Assets:
Derivative asset	0	0
Level 1 | Forward starting interest rate swaps
Other liabilities:
Derivative liabilities	0	0
Level 2
Assets:
Total	2,349	1,226
Other liabilities:
Total	5,146	1,689
Level 2 | Fixed income securities
Assets:
Debt securities, available-for-sale	444	442
Level 2 | Interest rate swaps
Assets:
Derivative asset	1,874	568
Other liabilities:
Derivative liabilities	344	173
Level 2 | Cross currency swaps
Assets:
Derivative asset		211
Other liabilities:
Derivative liabilities	3,651	912
Level 2 | Foreign exchange forwards
Assets:
Derivative asset	31	5
Level 2 | Forward starting interest rate swaps
Other liabilities:
Derivative liabilities	1,151	604
Level 3
Assets:
Total	0	0
Other liabilities:
Total	0	0
Level 3 | Fixed income securities
Assets:
Debt securities, available-for-sale	0	0
Level 3 | Interest rate swaps
Assets:
Derivative asset	0	0
Other liabilities:
Derivative liabilities	0	0
Level 3 | Cross currency swaps
Assets:
Derivative asset		0
Other liabilities:
Derivative liabilities	0	0
Level 3 | Foreign exchange forwards
Assets:
Derivative asset	0	0
Level 3 | Forward starting interest rate swaps
Other liabilities:
Derivative liabilities	$ 0	$ 0