Comprehensive Income - Summary of Comprehensive Income Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Amounts Reclassified Out Of Accumulated Other Comprehensive Income Loss [Abstract]
Beginning balance, Gains/(losses) on Cash Flow Hedges	$ (2,417)	$ (3,556)	$ (2,515)	$ (3,733)
Other comprehensive income/(loss) before reclassification, Gains/(losses) on Cash Flow Hedges	29	726	127	904
Amounts reclassified from AOCI, Gains/(losses) on Cash Flow Hedges
Fair Value adjustment on derivatives, net of tax	29	726	127	904
Ending balance, Gains/(losses) on Cash Flow Hedges	(2,388)	(2,830)	(2,388)	(2,830)
Beginning balance, Unrealized gains/(losses) on available-for-sale securities	12,719	27,327	7,608	29,464
Other comprehensive income/(loss) before reclassification, Unrealized gains/(losses) on available-for-sale securities	5,675	(14,199)	10,850	(16,160)
Amounts reclassified from AOCI, Unrealized gains/(losses) on available-for-sale securities		(131)	(63)	(308)
Net current period OCI, Unrealized gains/(losses) on available-for-sale securities	5,675	(14,330)	10,787	(16,468)
Ending Balance, Unrealized gains/(losses) on available-for-sale securities	18,394	12,997	18,394	12,997
Beginning balance, Defined benefit pension plan items	(455)	(604)	(478)	(628)
Other comprehensive income/(loss) before reclassification, Defined benefit pension plan items
Amounts reclassified from AOCI, Defined benefit pension plan items	22	24	44	48
Net current period OCI, Defined benefit pension plan items	22	24	44	48
Ending balance, Defined benefit pension plan items	(433)	(580)	(433)	(580)
Beginning balance, Total	9,847	23,167	4,615	25,103
Other comprehensive income/(loss) before reclassification, Total	5,704	(13,473)	10,977	(15,256)
Amounts reclassified from AOCI, Total	22	(107)	(19)	(260)
Net current period OCI, Total	5,726	(13,580)	10,958	(15,516)
Ending balance, Total	$ 15,573	$ 9,587	$ 15,573	$ 9,587