Borrowings - Schedule of Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Revolving Facility	$ 169,579	$ 195,000
Total borrowings	1,020,873	847,436
Less current portion	1,046	1,087
Less deferred debt issuance costs	4,399	5,203
Less unaccreted debt discount	1,193	1,439
Long-term borrowings	1,014,235	839,707
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	0
Senior Notes | 3.37% Senior Notes, due June 2025
Debt Instrument [Line Items]
Total borrowings	100,000	0
Other Borrowings
Debt Instrument [Line Items]
Other borrowings	$ 1,294	$ 2,436