Leases - (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Lease terms
Option to extend		P20Y
Weighted-average remaining lease term		10 years	5 years
Weighted-average discount rate		4.90%	4.80%
Increase in Right-of-Use Asset		$ 114,989	$ 8,330	$ 73,575
Lease expense
Operating lease expense		22,927	20,345	19,499
Variable lease expense		4,769	3,780	3,132
Rent expense		$ 27,696	$ 24,125	$ 22,631
Weighted-average remaining lease term		10 years	5 years
Minimum
Lease terms
Remaining lease terms		1 year
Maximum
Lease terms
Remaining lease terms		11 years
LA1
Lease terms
Net Leased Space | ft²		170,000
Increase in net rentable space | ft²		17,238
Increase in Right-of-Use Asset		$ 109,600
Increase in operating lease liability		$ 109,100
US Colo Los Angeles California
Lease terms
Increase in Right-of-Use Asset	$ 5,300