Consolidated Statements of Cash Flows (Parenthetical)	12 Months Ended
	Dec. 31, 2017 USD ($)
Payments of borrowings included in investing activities	$ 755,200,000
Total payment of borrowings	1,100,000,000
Value, shares repurchased	1,302,100,000
ASR Program
Stock repurchase program, authorized amount	400,000,000.0
Value, shares repurchased	$ 320,000,000.0