Changes in Accumulated Other Comprehensive Income (Loss) by Component - Changes in Accumulated Other Comprehensive Income (loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (122)	$ (8,118)
Other comprehensive income (loss) before reclassifications	(925)	6,361
Amounts reclassified from accumulated other comprehensive loss to net income	0	(1,841)
Net current-period other comprehensive income (loss)	(925)	4,520
Ending balance	(1,047)	(3,598)
Unrealized Gains on Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,142	(8,118)
Other comprehensive income (loss) before reclassifications	243	5,929
Amounts reclassified from accumulated other comprehensive loss to net income	0	(1,841)
Net current-period other comprehensive income (loss)	243	4,088
Ending balance	1,385	(4,030)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,264)	0
Other comprehensive income (loss) before reclassifications	(1,168)	432
Amounts reclassified from accumulated other comprehensive loss to net income	0	0
Net current-period other comprehensive income (loss)	(1,168)	432
Ending balance	$ (2,432)	$ 432