Subsequent Events - Additional Information (Details) - USD ($)		1 Months Ended
	Apr. 01, 2018	Feb. 28, 2018	Dec. 31, 2017
5.72% Notes, due 2019
Subsequent Event [Line Items]
Convertible notes, interest rate			5.72%
Subsequent Event
Subsequent Event [Line Items]
Stock repurchase program, authorized amount		$ 500,000,000
Subsequent Event | 5.72% Notes, due 2019
Subsequent Event [Line Items]
Approved debt reduction amount		$ 500,000,000
Subsequent Event | Salaried And Retirement Savings Plan
Subsequent Event [Line Items]
Retirement savings plan, employer contribution, percent	3.00%
Retirement savings plan, additional employer contribution, percent	3.00%