Description of Business and Summary of Accounting Policies - Effect of Adoption of Standard on Condensed Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net income	$ 104,981	$ 91,129	$ 48,024
Changes in operating assets and liabilities, net		(7,143)	2,592
Net cash provided by operating activities		157,846	146,426
Net decrease in cash and cash equivalents	$ (2,526)	3,181	1,415
Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers | As Originally Reported
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net income		91,156	48,024
Changes in operating assets and liabilities, net		(7,170)	2,592
Net cash provided by operating activities		157,846	146,426
Net decrease in cash and cash equivalents		3,181	$ 1,415
Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers | Effect of Change
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Net income		(27)
Changes in operating assets and liabilities, net		$ 27