Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Restricted Stock Units	Restricted Stock Awards	Common Stock	Common Stock Restricted Stock Units	Common Stock Restricted Stock Awards	Additional Paid in Capital	Additional Paid in Capital Restricted Stock Units	Additional Paid in Capital Restricted Stock Awards	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2013	$ 696,500			$ 29,790			$ 488,177			$ 199,053	$ (20,520)
Changes in Stockholders' Equity
Comprehensive income	50,188									62,121	(11,933)
Cash dividends declared per share: $0.94 per share in 2014, $1.00 per share in 2015 and $1.06 per share in 2016	(29,528)									(29,528)
Issuance of common stock, net of issuance costs	76,175			2,875			73,300
Shares issued — stock options	931			44			887
Shares issued — directors' stock plans	438			18			420
Shares issued — restricted stock units/awards		$ (502)			$ 37			$ (539)
Share-based compensation expense	2,931			10			2,921
Ending balance at Dec. 31, 2014	797,133			32,774			565,166			231,646	(32,453)
Changes in Stockholders' Equity
Comprehensive income	90,251									86,830	3,421
Cash dividends declared per share: $0.94 per share in 2014, $1.00 per share in 2015 and $1.06 per share in 2016	(36,918)									(36,918)
Issuance of common stock and common stock equivalents in business combinations	159,904			5,183			154,721
Shares issued — stock options	2,157			135			2,022
Shares issued — directors' stock plans	316			11			305
Shares issued — restricted stock units/awards		(347)			54			(401)
Share-based compensation expense	3,478			11			3,467
Ending balance at Dec. 31, 2015	1,015,974			38,168			725,280			281,558	(29,032)
Changes in Stockholders' Equity
Comprehensive income	97,028									108,032	(11,004)
Cash dividends declared per share: $0.94 per share in 2014, $1.00 per share in 2015 and $1.06 per share in 2016	(49,389)									(49,389)
Issuance of common stock and common stock equivalents in business combinations	1,504,811			32,074			1,472,737
Shares issued — stock options	(427)			229			(656)
Shares issued — directors' stock plans	2,597			95			2,502
Shares issued — restricted stock units/awards		$ (1,065)	$ (1,455)		$ 60	$ (33)		$ (1,125)	$ (1,422)
Share-based compensation expense	13,452			6			13,446
Ending balance at Dec. 31, 2016	$ 2,581,526			$ 70,599			$ 2,210,762			$ 340,201	$ (40,036)