Borrowings - Schedule of Borrowings (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Jun. 13, 2016
Debt Instrument [Line Items]
Total borrowings	$ 850,931	$ 851,078
Less current portion	455	483
Less deferred debt issuance costs	1,441	1,593
Less unaccreted debt discount	598	667
Total long-term borrowings	$ 848,437	$ 848,335
4.50% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate	4.50%	4.50%
4.20% Senior Notes, due December 2021
Debt Instrument [Line Items]
Stated interest rate	4.20%	4.20%
3.20% Senior Notes, due June 2023
Debt Instrument [Line Items]
Stated interest rate	3.20%	3.20%
3.37% Senior Notes, due June 2025
Debt Instrument [Line Items]
Stated interest rate	3.37%	3.37%
Revolving Facility
Debt Instrument [Line Items]
Revolving Facility	$ 0	$ 0
Senior Notes | 4.50% Senior Notes, due December 2020
Debt Instrument [Line Items]
Total borrowings	300,000	300,000
Senior Notes | 4.20% Senior Notes, due December 2021
Debt Instrument [Line Items]
Total borrowings	350,000	350,000
Senior Notes | 3.20% Senior Notes, due June 2023
Debt Instrument [Line Items]
Total borrowings	100,000	100,000
Stated interest rate			3.20%
Senior Notes | 3.37% Senior Notes, due June 2025
Debt Instrument [Line Items]
Total borrowings	100,000	100,000
Stated interest rate			3.37%
Other borrowings
Debt Instrument [Line Items]
Other borrowings	$ 931	$ 1,078