Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jun. 30, 2018	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclass due to adopting Accounting Standard Update		$ 0
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in income tax expense	$ 1,048
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclass due to adopting Accounting Standard Update			$ 6,353
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total future minimum lease payments for operating leases	$ 69,844