Parent Company Financial Information (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net Income (Loss)	$ 26,740	$ 25,780	$ 21,946	$ 24,361	$ 18,920	$ 21,583	$ 21,227	$ 19,844	$ 98,827	$ 81,574	$ 60,016
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense									4,090	2,859	2,844
Net cash provided by operating activities									134,756	137,618	79,636
Net cash received (paid) in business combinations									0	32,255	(154,170)
Investing Activities
Net cash provided by investing activities									(423,054)	(521,961)	(281,060)
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock									(137)	(96)	(32)
Cash dividends paid									(77,263)	(49,494)	(19,858)
Proceeds from Warrant Exercises									0	5,000	0
Purchase and retirement of common stock									(906)	(622)	(429)
Proceeds from exercise of stock options									1,258	929	1,092
Excess tax benefit from stock-based compensation									0	205	1,203
Net cash provided by financing activities									275,430	392,952	(132,941)
Increase (decrease) in cash and cash equivalents									(12,868)	8,609	(334,365)
Cash and cash equivalents at beginning of period				188,170				179,561	188,170	179,561	513,926
Cash and cash equivalents at end of period	175,302				188,170				175,302	188,170	179,561
Parent Company [Member]
Operating Activities
Net Income (Loss)									98,827	81,574	60,016
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in (undistributed) excess distributed earnings of subsidiaries									(33,058)	(66,681)	119,533
Stock-based compensation expense									4,090	2,859	2,844
Net changes in other assets and liabilities									(3,170)	(403)	6,830
Net cash provided by operating activities									66,689	17,349	189,223
Net cash received (paid) in business combinations									0	10,277	(53,159)
Investing Activities
Net cash provided by investing activities									0	10,277	(53,159)
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock									(137)	(96)	(32)
Cash dividends paid									(77,263)	(49,494)	(19,858)
Repayment of long-term subordinated debt									(8,248)	(14,636)	(51,000)
Proceeds from Warrant Exercises									0	5,000	0
Purchase and retirement of common stock									(906)	(622)	(429)
Proceeds from exercise of stock options									1,258	929	1,092
Downstream stock offering proceeds to the Bank									0	0	(100,000)
Excess tax benefit from stock-based compensation									0	205	1,203
Net cash provided by financing activities									(85,296)	(58,714)	(169,024)
Increase (decrease) in cash and cash equivalents									(18,607)	(31,088)	(32,960)
Cash and cash equivalents at beginning of period				$ 22,596				$ 53,684	22,596	53,684	86,644
Cash and cash equivalents at end of period	$ 3,989				$ 22,596				$ 3,989	$ 22,596	$ 53,684