Accumulated Other Comprehensive Gain (Loss) - Activity within Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2015			$ 654,400
Other comprehensive income loss	$ (8,774)	$ (16,526)	(2,659)	$ (31,515)
Balance at June 30, 2016	695,638		695,638
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at December 31, 2015			(71,576)
Balance at June 30, 2016	$ (74,235)		$ (74,235)