Other Assets - Summary of Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Debt issue costs, net	$ 7,093	$ 4,478
Equity investments	288,398	177,430
Other corporate assets	117,827	77,580
Prepaids and other assets	55,176	44,285
Total other assets	$ 468,494	$ 303,773