Common Stock Repurchase Programs - Additional Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended
	Jul. 31, 2019	May 31, 2019	Feb. 28, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Jul. 30, 2019	May 31, 2018	Apr. 30, 2016
Share Repurchases [Line Items]
Accelerated share repurchase (shares)				161
Repurchased				$ 49,504	$ 99,504	$ 100,000
Payments for repurchase of common stock					99,504	$ 100,000
April 2016 Repurchase Program
Share Repurchases [Line Items]
Accelerated share repurchase (shares)							700	200
Share repurchase price (in dollars per share)							$ 293.21	$ 243.40
Repurchased							$ 200,000	$ 50,000
Value of repurchased common stock											$ 300,000
2017 ASR
Share Repurchases [Line Items]
Accelerated share repurchase (shares)								400
Price ($ per share)								$ 146.48
Repurchased								$ 50,000
May 2018 Repurchase Program
Share Repurchases [Line Items]
Accelerated share repurchase (shares)		200	200				100
Share repurchase price (in dollars per share)		$ 307.48	$ 243.42				$ 356.54
Repurchased		$ 49,500	$ 50,000				$ 50,000
Remaining shares under repurchase program				$ 400,500	$ 400,500
Value of repurchased common stock										$ 600,000
2018 ASR
Share Repurchases [Line Items]
Accelerated share repurchase (shares)							200
Share repurchase price (in dollars per share)							$ 213.18
Repurchased							$ 50,000
Subsequent Event | 2019 ASR
Share Repurchases [Line Items]
Value of repurchased common stock									$ 200,000
Payments for repurchase of common stock	$ 200,000
Common stock repurchased (in shares)	700