Accumulated Other Comprehensive Income - Activity in Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income [Line Items]
Balance at beginning of period	$ (9,380)	$ 5,418
Other comprehensive (loss) income before reclassification	5,292	(314)
Reclassification from accumulated other comprehensive income	(1,421)	(9)
Other comprehensive income (loss)	3,871	(323)
Balance at end of period	(5,509)	5,095
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income [Line Items]
Balance at beginning of period	(18,187)	7,348
Other comprehensive (loss) income before reclassification	8,098	(568)
Reclassification from accumulated other comprehensive income	(1,421)	(9)
Other comprehensive income (loss)	6,677	(577)
Balance at end of period	(11,510)	6,771
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Interest-Only Strip [Member]
Accumulated Other Comprehensive Income [Line Items]
Balance at beginning of period	16	16
Other comprehensive (loss) income before reclassification	1	3
Reclassification from accumulated other comprehensive income
Other comprehensive income (loss)	1	3
Balance at end of period	17	19
Tax (Expense) Benefit [Member]
Accumulated Other Comprehensive Income [Line Items]
Balance at beginning of period	8,791	(1,946)
Other comprehensive (loss) income before reclassification	(2,807)	251
Reclassification from accumulated other comprehensive income
Other comprehensive income (loss)	(2,807)	251
Balance at end of period	$ 5,984	$ (1,695)