Derivatives - Additional Information (Detail)	Mar. 31, 2018 USD ($) derivative	Mar. 31, 2017 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Number of derivative financial instruments | derivative	29
Combined notional amount	$ 2,145,132,000
Estimated amount of unrealized gains or losses expected to be reclassified as interest expense in next fiscal year	$ (12,124,000)	$ (12,124)