Recently Adopted Accounting Standard - Schedule of Previously Reported Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income taxes	$ 15,760	$ 12,432	$ 29,506	$ 25,170
Net income	$ 28,782	$ 23,725	$ 56,732	$ 47,430
Basic net income per share	$ 0.98	$ 0.81	$ 1.93	$ 1.61
Diluted net income per share	$ 0.97	$ 0.80	$ 1.92	$ 1.60
Diluted weighted average common shares outstanding	29,550,418	29,477,870	29,555,985	29,694,081
Cash flows provided by operating activities			$ 119	$ 16,442
Cash flows used in financing activities			$ (3,082)	(19,051)
As Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Provision for income taxes		$ 12,878		25,919
Net income		$ 23,279		$ 46,681
Basic net income per share		$ 0.80		$ 1.58
Diluted net income per share		$ 0.79		$ 1.57
Diluted weighted average common shares outstanding		29,423,845		29,642,287
Cash flows provided by operating activities				$ 15,632
Cash flows used in financing activities				$ (18,241)