Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Income (AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	$ 3,628	$ (1,055)	$ 2,810	$ (4,295)
Other comprehensive income/(loss) before reclassification	(2,130)	3,143	(1,628)	6,120
Amounts reclassified from accumulated other comprehensive income	554	(127)	870	136
Net current period other comprehensive income/(loss)	(1,576)	3,016	(758)	6,256
Ending balance	$ 2,052	$ 1,961	$ 2,052	$ 1,961