Earnings Per Share - Computation of Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Allocation of net income (loss) to common stock	$ 42,042	$ 37,298
Earnings (loss) per share:
Common stock-basic (usd per share)	$ 0.73	$ 0.64
Common Stock [Member]
Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Allocation of net income (loss) to common stock	$ 41,845	$ 37,100
Weighted average number of common shares:
Weighted average number (shares)	57,679,041	58,190,819
Unvested Participating Shares [Member]
Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Allocation of net income (loss) to common stock	$ 197	$ 198
Weighted average number of common shares:
Weighted average number (shares)	271,153	310,888