Note 10 - Fair Value of Financial Instruments (Detail) - Fair value measured on a recurring basis: (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets, carried at fair value on a recurring basis	$ 1,000,361	$ 949,588
Liabilities, carried at fair value on a recurring basis	25,880	25,844
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member]
Assets, carried at fair value on a recurring basis	740,940	696,638
Fair Value, Inputs, Level 2 [Member] | Other securities [Member]
Assets, carried at fair value on a recurring basis	218,788	213,374
Fair Value, Inputs, Level 2 [Member] | Interest rate caps [Member]
Assets, carried at fair value on a recurring basis	16	19
Fair Value, Inputs, Level 2 [Member] | Interest rate swaps [Member]
Assets, carried at fair value on a recurring basis	51	3
Liabilities, carried at fair value on a recurring basis	1,138	1,922
Fair Value, Inputs, Level 2 [Member]
Assets, carried at fair value on a recurring basis	959,795	910,034
Liabilities, carried at fair value on a recurring basis	1,138	1,922
Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member]
Assets, carried at fair value on a recurring basis	23,761	23,475
Fair Value, Inputs, Level 3 [Member] | Other securities [Member]
Assets, carried at fair value on a recurring basis	16,805	16,079
Fair Value, Inputs, Level 3 [Member] | Borrowings [Member]
Liabilities, carried at fair value on a recurring basis	24,742	23,922
Fair Value, Inputs, Level 3 [Member]
Assets, carried at fair value on a recurring basis	40,566	39,554
Liabilities, carried at fair value on a recurring basis	24,742	23,922
Collateralized Mortgage Backed Securities [Member]
Assets, carried at fair value on a recurring basis	764,701	720,113
Other securities [Member]
Assets, carried at fair value on a recurring basis	235,593	229,453
Interest rate caps [Member]
Assets, carried at fair value on a recurring basis	16	19
Interest rate swaps [Member]
Assets, carried at fair value on a recurring basis	51	3
Liabilities, carried at fair value on a recurring basis	1,138	1,922
Borrowings [Member]
Liabilities, carried at fair value on a recurring basis	$ 24,742	$ 23,922