Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	3,343,000	1,616,000
Dollar Amount Purchased in 2018	$ 274,500	$ 93,000
Stock repurchase program, average cost per share (in dollars per share)	$ 82.12	$ 57.56
Dollar Amount Authorized	$ 100,000
Remaining Dollar Amount Authorized For Future Purchases	142,760
Payments of dividends	$ 40,853	$ 36,836	$ 19,808
May 15, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	239,000
Dollar Amount Purchased in 2018	$ 17,300
Remaining Dollar Amount Authorized For Future Purchases	$ 0
October 24, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	1,282,000
Dollar Amount Purchased in 2018	$ 100,000
Remaining Dollar Amount Authorized For Future Purchases	$ 0
April 25, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	1,098,000
Dollar Amount Purchased in 2018	$ 100,000
Remaining Dollar Amount Authorized For Future Purchases	$ 0
July 25, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	724,000
Dollar Amount Purchased in 2018	$ 57,200
Remaining Dollar Amount Authorized For Future Purchases	$ 42,760
October 24, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)	0
Dollar Amount Purchased in 2018	$ 0
Remaining Dollar Amount Authorized For Future Purchases	$ 100,000