Leases - (Detail) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) ft²	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) ft²	Sep. 30, 2017 USD ($)	Apr. 20, 2018 ft²	Dec. 31, 2017
Lease terms
Option to extend				P20Y
Weighted-average remaining lease term		10 years		10 years			5 years
Weighted-average discount rate		4.90%		4.90%			4.80%
Increase in Right-of-Use Asset				$ 114,989	$ 8,330
Lease expense
Operating lease expense		$ 6,144	$ 5,078	16,789	15,256
Variable lease expense		1,185	999	3,487	2,714
Rent expense		$ 7,329	$ 6,077	$ 20,276	$ 17,970
Weighted-average remaining lease term		10 years		10 years			5 years
Minimum
Lease terms
Remaining lease terms		1 year		1 year
Maximum
Lease terms
Remaining lease terms		11 years		11 years
LA1
Lease terms
Net rentable space | ft²		170,000		170,000
Increase in net rentable space | ft²		17,238		17,238
Increase in Right-of-Use Asset				$ 109,600
Increase in operating lease liability				$ 109,100
US Colo Los Angeles California
Lease terms
Net rentable space | ft²						6,723
Increase in Right-of-Use Asset	$ 5,300