Shareholders' Equity (Details) - USD ($) shares in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	May 31, 2019
Class of Stock [Line Items]
Dividends	$ 30,633,000	$ 30,831,000	$ 25,915,000	$ 26,051,000	$ 61,500,000	$ 52,000,000.0
Payments for repurchase of common stock					$ 118,824,000	$ 112,491,000
Increase in share repurchase authorization							$ 500,000,000.0
Share repurchase plan
Class of Stock [Line Items]
Share repurchases (shares)					3.5	3.5
Payments for repurchase of common stock					$ 108,500,000	$ 105,100,000
Remaining value of stock repurchase programs authorization	$ 691,400,000				691,400,000
Shares withheld to pay taxes
Class of Stock [Line Items]
Payments for repurchase of common stock					$ 10,400,000	$ 7,400,000