Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jan. 01, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Corporate bonds	$ 39,157	$ 38,399	$ 30,011
Level 1 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Deferred compensation plan assets	64,435	60,290
Corporate bonds	39,157	38,399
Level 2 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Interest rate swap		(126)
Level 3 [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Contingent purchase price liabilities	$ (30,611)	$ (33,368)