Condensed Financial Statements of Parent Company - Condensed balance sheet - (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS.
Cash	$ 695,794	$ 417,869	$ 479,461	$ 380,864
Investment securities available for sale	1,009,541	806,766
Other Assets	61,239	71,774
Total assets	8,557,348	7,826,227
Liabilities.	7,497,964	6,841,307
Shareholders' equity	1,059,384	984,920	981,469	507,549
Total liabilities and shareholders' equity	8,557,348	7,826,227
Parent company
ASSETS.
Cash	21,592	13,185	$ 11,757	$ 6,122
Investment securities available for sale	646	535
Investment in subsidiaries	1,090,719	1,072,796
Other Assets	1,353	1,023
Total assets	1,114,310	1,087,539
Liabilities.	54,926	102,619
Shareholders' equity	1,059,384	984,920
Total liabilities and shareholders' equity	$ 1,114,310	$ 1,087,539