Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Detail) - Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Money market and mutual funds	$ 162,906
Derivative financial instruments	18,298	$ 6,318
Total	181,204	6,318
Liabilities
Derivative financial instruments	877	2,258
Fair value of earn-out consideration	920
Total	1,797	2,258
Level 1
Assets
Money market and mutual funds	162,906	0
Total	162,906	0
Liabilities
Fair value of earn-out consideration	0
Level 2
Assets
Money market and mutual funds	0
Derivative financial instruments	18,298	6,318
Total	18,298	6,318
Liabilities
Derivative financial instruments	877	2,258
Fair value of earn-out consideration	0
Total	877	2,258
Level 3
Assets
Money market and mutual funds	0
Liabilities
Derivative financial instruments	0	$ 0
Fair value of earn-out consideration	920
Total	$ 920