Borrowings (Schedule of Borrowings) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Total borrowings	$ 1,106,692	$ 847,436
Less current portion	1,171	1,087
Less deferred debt issuance costs	4,664	5,203
Less unaccreted debt discount	1,256	1,439
Total long-term borrowings	1,099,601	839,707
Revolving Facility
Debt Instrument [Line Items]
Revolving Facility	255,130	195,000
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	$ 1,562	$ 2,436