Parent Company Financial Information (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities
Net income	$ 30,718	$ 27,484	$ 25,405	$ 21,259	$ 26,740	$ 25,780	$ 21,946	$ 24,361	$ 104,866	$ 98,827	$ 81,574
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense									5,009	4,090	2,859
Net cash provided by operating activities									145,847	134,756	137,618
Net cash received in business combinations									0	0	32,255
Investing Activities
Net cash provided by investing activities									(548,553)	(423,054)	(521,961)
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock									(157)	(137)	(96)
Cash dividends paid									(88,677)	(77,263)	(49,494)
Proceeds from Warrant Exercises									0	0	5,000
Purchase and retirement of common stock									(1,125)	(906)	(622)
Proceeds from exercise of stock options									1,349	1,258	929
Excess tax benefit from stock-based compensation									344	0	205
Net cash provided by financing activities									451,642	275,430	392,952
Increase (decrease) in cash and cash equivalents									48,936	(12,868)	8,609
Cash and cash equivalents at beginning of period				175,302				188,170	175,302	188,170	179,561
Cash and cash equivalents at end of period	224,238				175,302				224,238	175,302	188,170
Parent Company [Member]
Operating Activities
Net income									104,866	98,827	81,574
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries									(22,757)	(33,058)	(66,681)
Stock-based compensation expense									5,009	4,090	2,859
Net changes in other assets and liabilities									(394)	(3,170)	(403)
Net cash provided by operating activities									86,724	66,689	17,349
Net cash received in business combinations									0	0	10,277
Investing Activities
Net cash provided by investing activities									0	0	10,277
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock									(157)	(137)	(96)
Cash dividends paid									(88,677)	(77,263)	(49,494)
Repayment of long-term subordinated debt									0	(8,248)	(14,636)
Proceeds from Warrant Exercises									0	0	5,000
Purchase and retirement of common stock									(1,125)	(906)	(622)
Proceeds from exercise of stock options									1,349	1,258	929
Excess tax benefit from stock-based compensation									344	0	205
Net cash provided by financing activities									(88,266)	(85,296)	(58,714)
Increase (decrease) in cash and cash equivalents									(1,542)	(18,607)	(31,088)
Cash and cash equivalents at beginning of period				$ 3,989				$ 22,596	3,989	22,596	53,684
Cash and cash equivalents at end of period	$ 2,447				$ 3,989				$ 2,447	$ 3,989	$ 22,596