Borrowings (Additional Information) (Detail)		9 Months Ended
	Jun. 23, 2015 USD ($)	Sep. 30, 2016 USD ($) covenant	Jun. 13, 2016 USD ($)	Dec. 31, 2015 USD ($)
Minimum
Line of Credit Facility [Line Items]
Required percent for prepayment amount of aggregate principal amount			5.00%
Revolving Facility
Line of Credit Facility [Line Items]
Current borrowings under revolving facility		$ 255,130,000		$ 195,000,000
Outstanding letters of credit		8,200,000
Revolving Facility, amount available to borrow		$ 436,700,000
Number of financial covenants | covenant		2
Other borrowings
Line of Credit Facility [Line Items]
Other borrowings		$ 1,562,000		$ 2,436,000
Other borrowings | Minimum
Line of Credit Facility [Line Items]
Stated interest rate		0.90%
Other borrowings | Maximum
Line of Credit Facility [Line Items]
Stated interest rate		2.83%
Senior Notes | Minimum
Line of Credit Facility [Line Items]
Interest coverage ratio		3.0
Senior Notes | Maximum
Line of Credit Facility [Line Items]
Limitation of outstanding principal of higher preference debt as percent of consolidated assets		15.00%
Leverage ratio		3.50
3.2% Senior Notes, due June 2023
Line of Credit Facility [Line Items]
Stated interest rate		3.20%
3.2% Senior Notes, due June 2023 | Senior Notes
Line of Credit Facility [Line Items]
Face amount of debt			$ 100,000,000
Stated interest rate			3.20%
3.37% Senior Notes, due June 2025
Line of Credit Facility [Line Items]
Stated interest rate		3.37%
3.37% Senior Notes, due June 2025 | Senior Notes
Line of Credit Facility [Line Items]
Face amount of debt			$ 100,000,000
Stated interest rate			3.37%
4.5% Senior Notes, due December 2020
Line of Credit Facility [Line Items]
Stated interest rate		4.50%
4.2% Senior Notes, due December 2021
Line of Credit Facility [Line Items]
Stated interest rate		4.20%
Credit Agreement
Line of Credit Facility [Line Items]
Debt instrument, term	5 years
Borrowing capacity	$ 700,000,000
Expiration date	Jun. 23, 2020
Extension period	1 year
Aggregate lending commitments	$ 350,000,000
Applicable margin over LIBOR		1.10%
Effective percentage		1.34%
Credit Agreement | Minimum
Line of Credit Facility [Line Items]
Applicable margin over LIBOR		0.005%
Credit Agreement | Maximum
Line of Credit Facility [Line Items]
Applicable margin over LIBOR		1.50%
Credit Agreement | Letters Of Credit
Line of Credit Facility [Line Items]
Borrowing capacity	75,000,000
Credit Agreement | Swing line Loans
Line of Credit Facility [Line Items]
Borrowing capacity	$ 50,000,000