Changes in Accumulated Other Comprehensive Income (Loss) By Component (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), Net of Tax [Roll Forward]
Beginning balance			$ 553,902	$ 443,145
Ending balance	$ 680,562	$ 523,501	680,562	523,501
Unrealized Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(363)	1,277	(4,602)	1,156
Other comprehensive income (loss) before reclassifications	5,258	(3,147)	9,513	(3,026)
Amounts reclassified from accumulated other comprehensive loss to net income	0	43	(16)	43
Net current-period other comprehensive income (loss)	5,258	(3,104)	9,497	(2,983)
Ending balance	4,895	(1,827)	4,895	(1,827)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(547)	108	(584)	(14)
Other comprehensive income (loss) before reclassifications	(221)	(242)	(184)	(120)
Amounts reclassified from accumulated other comprehensive loss to net income	0	0	0	0
Net current-period other comprehensive income (loss)	(221)	(242)	(184)	(120)
Ending balance	(768)	(134)	(768)	(134)
Total Unrealized Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(910)	1,385	(5,186)	1,142
Other comprehensive income (loss) before reclassifications	5,037	(3,389)	9,329	(3,146)
Amounts reclassified from accumulated other comprehensive loss to net income	0	43	(16)	43
Net current-period other comprehensive income (loss)	5,037	(3,346)	9,313	(3,103)
Ending balance	4,127	(1,961)	4,127	(1,961)
Unrealized Loss on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(4,423)	(2,432)	(2,798)	(1,264)
Other comprehensive income (loss) before reclassifications	(508)	279	(2,133)	(889)
Amounts reclassified from accumulated other comprehensive loss to net income	377	0	377	0
Net current-period other comprehensive income (loss)	(131)	279	(1,756)	(889)
Ending balance	(4,554)	(2,153)	(4,554)	(2,153)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(5,333)	(1,047)	(7,984)	(122)
Other comprehensive income (loss) before reclassifications	4,529	(3,110)	7,196	(4,035)
Amounts reclassified from accumulated other comprehensive loss to net income	377	43	361	43
Net current-period other comprehensive income (loss)	4,906	(3,067)	7,557	(3,992)
Ending balance	$ (427)	$ (4,114)	$ (427)	$ (4,114)