Note 21 - Regulatory Matters - Capital and Leverage Ratios (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Company [Member]
Common equity Tier 1 capital ( to risk-weighted assets)		$ 1,459,351	$ 1,383,377
Common equity Tier 1 capital ( to risk-weighted assets)		12.84%	12.95%
Common equity Tier 1 capital minimum requirement		$ 511,590	$ 480,830
Common equity Tier 1 capital minimum requirement		4.50%	4.50%
Excess Common equtiy Tier 1 capital		$ 947,761	$ 902,547
Excess Common equtiy Tier 1 capital		8.34%	8.45%
Tier 1 capital (to risk-weighted assets)		$ 1,574,806	$ 1,498,810
Tier 1 capital (to risk-weighted assets)		13.85%	14.03%
Tier 1 capital minimum requirement		$ 682,120	$ 641,107
Tier 1 capital minimum requirement		6.00%	6.00%
Excess Tier 1 capital		$ 892,686	$ 857,703
Excess Tier 1 capital		7.85%	8.03%
Total capital (to risk-weighted assets)		$ 1,702,144	$ 1,634,631
Total capital (to risk-weighted assets)		14.97%	15.30%
Total capital minimum requirement		$ 909,493	$ 854,809
Total capital minimum requirement		8.00%	8.00%
Excess Total capital		$ 792,651	$ 779,822
Excess Total capital		6.97%	7.30%
Tier 1 capital (to average assets) – Leverage ratio		$ 1,574,806	$ 1,498,810
Tier 1 capital (to average assets) – Leverage ratio		11.57%	11.95%
Minimum leverage requirement		$ 544,614	$ 501,875
Minimum leverage requirement		4.00%	4.00%
Excess Tier One Leverage Capital		$ 1,030,192	$ 996,935
Excess Tier One Leverage Capital		7.57%	7.95%
Risk-weighted assets		$ 11,368,663	$ 10,685,115
Total average assets (1)	[1]	13,615,348	12,546,879
Bank [Member]
Common equity Tier 1 capital ( to risk-weighted assets)		$ 1,515,096	$ 1,443,159
Common equity Tier 1 capital ( to risk-weighted assets)		13.35%	13.54%
Common equity Tier 1 capital minimum requirement		$ 510,582	$ 479,801
Common equity Tier 1 capital minimum requirement		4.50%	4.50%
Excess Common equtiy Tier 1 capital		$ 1,004,514	$ 963,358
Excess Common equtiy Tier 1 capital		8.85%	9.04%
Tier 1 capital (to risk-weighted assets)		$ 1,515,096	$ 1,443,159
Tier 1 capital (to risk-weighted assets)		13.35%	13.54%
Tier 1 capital minimum requirement		$ 680,776	$ 639,735
Tier 1 capital minimum requirement		6.00%	6.00%
Excess Tier 1 capital		$ 834,320	$ 803,424
Excess Tier 1 capital		7.35%	7.54%
Total capital (to risk-weighted assets)		$ 1,637,286	$ 1,576,525
Total capital (to risk-weighted assets)		14.43%	14.79%
Total capital minimum requirement		$ 907,701	$ 852,980
Total capital minimum requirement		8.00%	8.00%
Excess Total capital		$ 729,585	$ 723,545
Excess Total capital		6.43%	6.79%
Tier 1 capital (to average assets) – Leverage ratio		$ 1,515,096	$ 1,443,159
Tier 1 capital (to average assets) – Leverage ratio		11.16%	11.53%
Minimum leverage requirement		$ 543,059	$ 500,455
Minimum leverage requirement		4.00%	4.00%
Excess Tier One Leverage Capital		$ 972,037	$ 942,704
Excess Tier One Leverage Capital		7.16%	7.53%
Risk-weighted assets		$ 11,346,260	$ 10,662,248
Total average assets (1)	[1]	$ 13,576,477	$ 12,511,382

[1] The quarterly total average assets reflect all debt securities at amortized cost, equity security with readily determinable fair values at the lower of cost or fair value, and equity securities without readily determinable fair values at historical cost.