Recently Adopted Accounting Standard - Schedule of Previously Reported Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income taxes	$ 10,208	$ 2,702	$ 39,715	$ 27,871
Net income	$ 20,098	$ 7,787	$ 76,829	$ 55,217
Basic net income per share	$ 0.68	$ 0.27	$ 2.61	$ 1.88
Diluted net income per share	$ 0.68	$ 0.26	$ 2.60	$ 1.86
Diluted weighted average common shares outstanding	29,578,216	29,516,718	29,563,497	29,635,796
Cash flows provided by operating activities			$ 92,837	$ 83,579
Cash flows used in financing activities			$ (3,329)	(62,452)
As Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income taxes		$ 3,591		29,510
Net income		$ 6,898		$ 53,578
Basic net income per share		$ 0.24		$ 1.82
Diluted net income per share		$ 0.23		$ 1.81
Diluted weighted average common shares outstanding		29,457,653		29,581,578
Cash flows provided by operating activities				$ 81,880
Cash flows used in financing activities				$ (60,573)