Borrowings - Schedule of Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jun. 13, 2016	Dec. 09, 2011	Dec. 06, 2010
Debt Instrument [Line Items]
Total borrowings	$ 850,622	$ 851,078
Less current portion	388	483
Less deferred debt issuance costs	983	1,593
Less unaccreted debt discount	387	667
Long-term borrowings	848,864	848,335
Revolving Credit Facility
Debt Instrument [Line Items]
Total borrowings	$ 0	$ 0
4.50% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate	4.50%	4.50%			4.50%
4.20% Senior Notes, due December 2021
Debt Instrument [Line Items]
Stated interest rate	4.20%	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%
Senior Notes | 4.50% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate	4.50%
Total borrowings	$ 300,000	$ 300,000
Senior Notes | 4.20% Senior Notes, due December 2021
Debt Instrument [Line Items]
Stated interest rate	4.20%
Total borrowings	$ 350,000	350,000
Senior Notes | 3.20% Senior Notes, due June 2023
Debt Instrument [Line Items]
Stated interest rate	3.20%		3.20%
Total borrowings	$ 100,000	100,000
Senior Notes | 3.37% Senior Notes, due June 2025
Debt Instrument [Line Items]
Stated interest rate	3.37%		3.37%
Total borrowings	$ 100,000	100,000
Other Borrowings
Debt Instrument [Line Items]
Total borrowings	$ 622	$ 1,078