Debt and Credit Facilities (Tables)

12 Months Ended

Apr. 30, 2018

Debt Disclosure [Abstract]

Schedule of long-term debt

Our long-term debt (net of unamortized discounts and issuance costs) consisted of:

April 30,	2017		2018
1.00% senior notes, $250 principal amount, due January 15, 2018	$	249	$	—
2.25% senior notes, $250 principal amount, due January 15, 2023	248		248
3.50% senior notes, $300 principal amount, due April 15, 2025	—		296
1.20% senior notes, €300 principal amount, due July 7, 2026	324		361
2.60% senior notes, £300 principal amount, due July 7, 2028	383		408
4.00% senior notes, $300 principal amount, due April 15, 2038	—		293
3.75% senior notes, $250 principal amount, due January 15, 2043	248		248
4.50% senior notes, $500 principal amount, due July 15, 2045	486		487
	1,938		2,341
Less current portion	249		—
	$	1,689	$	2,341