Borrowings - Schedule of Borrowings (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Jun. 13, 2016
Debt Instrument [Line Items]
Total borrowings	$ 863,488	$ 862,186
Less current portion	835	258
Less deferred debt issuance costs	2,052	2,204
Less unaccreted debt discount	870	936
Total long-term borrowings	$ 859,731	858,788
4.5% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate	4.50%
4.2% Senior Notes, due December 2021
Debt Instrument [Line Items]
Stated interest rate	4.20%
3.2% Senior Notes, due June 2023
Debt Instrument [Line Items]
Stated interest rate	3.20%
3.37% Senior Notes, due June 2025
Debt Instrument [Line Items]
Stated interest rate	3.37%
Revolving Facility
Debt Instrument [Line Items]
Revolving Facility	$ 11,079	10,740
Senior Notes | 4.5% Senior Notes, due December 2020
Debt Instrument [Line Items]
Total borrowings	300,000	300,000
Senior Notes | 4.2% Senior Notes, due December 2021
Debt Instrument [Line Items]
Total borrowings	350,000	350,000
Senior Notes | 3.2% 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	$ 2,409	$ 1,446