Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2017	[1]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Current:
Federal										$ (3,690)		$ 4,981		$ 174
State and local										532		567		2
Current Income Tax Expense (Benefit), Total										(3,158)		5,548		176
Deferred:
Federal										4,293		949		2,460
State and local										(288)		131		308
Deferred Income Tax Expense (Benefit)										4,005		1,080		2,768
Expense for income taxes	$ (7,389)		$ (652)	$ 5,314	$ 3,574	$ (1,071)	$ 2,933	$ 2,962	$ 1,804	$ 847	[2]	$ 6,628	[2]	$ 2,944

[1] As discussed previously, the fourth quarter 2017 results include the results of ARI subsequent to the acquisition on October 10, 2017.

[2] The sum of the net earnings per share may not add up to the full year amount due to rounding and because the quarterly calculations are based on varying numbers of shares outstanding.