Derivative Instruments and Hedging Activities - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated other comprehensive income (loss):
Beginning Balance	$ 287,466
Ending Balance	269,681
Gains (Losses) on Cash Flow Hedges [Member]
Accumulated other comprehensive income (loss):
Beginning Balance	(5,076)
Other comprehensive income before reclassifications	11,597
Amounts reclassified from accumulated other comprehensive income to interest expense	(1,630)
Unrealized gain on derivatives, net of tax	9,967
Ending Balance	3,797
Gains (Losses) on Cash Flow Hedges [Member] | ASU 2018-02 [Member]
Accumulated other comprehensive income (loss):
Impact of adoption of ASU 2018-02	$ (1,094)