Treasury Stock - Treasury Stock Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended				6 Months Ended		12 Months Ended
	Mar. 18, 2016	Sep. 16, 2015	May 15, 2015	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Treasury Stock [Roll Forward]
Beginning balance (shares)				3,446,208	2,395,049	2,164	0	2,395,049	0	0
Beginning balance				$ 65,505	$ 48,479	$ 37	$ 0	$ 48,479	$ 0	$ 0
Ending balance (shares)				3,678,188	3,446,208	915,364	2,164	3,678,188	915,364	2,395,049	0
Ending balance				$ 70,489	$ 65,505	$ 20,036	$ 37	$ 70,489	$ 20,036	$ 48,479	$ 0
Average share price (usd per share)				$ 19.1640	$ 19.0079	$ 21.8889	$ 17.2000	$ 19.1640	$ 21.8889	$ 20.2411	$ 0.0000
Repurchases on open market
Treasury Stock [Roll Forward]
Shares repurchased (shares)				231,980		0		383,139	2,164
Shares repurchased				$ 4,984		$ 0		$ 7,520	$ 37
Average share price (usd per share)				$ 21.4828		$ 0.0000		$ 19.6282	$ 17.2000
Repurchase from LSF8 in private transaction
Treasury Stock [Roll Forward]
Shares repurchased (shares)	900,000	1,007,500	913,200	0		913,200		900,000	913,200
Shares repurchased	$ 14,500	$ 20,000	$ 20,000	$ 0		$ 19,999		$ 14,490	$ 19,999
Average share price (usd per share)	$ 16.10	$ 19.85	$ 21.90	$ 0.0000		$ 21.9000		$ 16.1000	$ 21.9000