Changes to Accumulated Other Comprehensive Income (Loss) by Component (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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			$ 148,766
Total other comprehensive income (loss)	6,905	(24,600)	18,791	(20,049)
Balance at End of Period	167,557		167,557
Net unrealized gains on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	185,275	183,603	164,654	186,580
Other comprehensive income (loss) before reclassifications	12,721	(38,012)	33,229	(28,982)
Amounts reclassified from other accumulated comprehensive income	(454)	(242)	(341)	(12,249)
Total other comprehensive income (loss)	12,267	(38,254)	32,888	(41,231)
Balance at End of Period	197,542	145,349	197,542	145,349
Net unrealized losses on interest rate agreements accounted for as cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(24,623)	(40,720)	(15,888)	(48,248)
Other comprehensive income (loss) before reclassifications	(5,401)	13,585	(14,196)	21,025
Amounts reclassified from other accumulated comprehensive income	39	69	99	157
Total other comprehensive income (loss)	(5,362)	13,654	(14,097)	21,182
Balance at End of Period	$ (29,985)	$ (27,066)	$ (29,985)	$ (27,066)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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