Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified		Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
BALANCE, VALUE at Dec. 31, 2011		$ 1,672,413	$ 1,514,913	$ 123,726	$ 33,774
BALANCE, SHARES at Dec. 31, 2011			112,164,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		101,891		101,891
Other comprehensive income (loss), net of tax		(9,428)			(9,428)
Stock-based compensation		4,041	4,041
Stock repurchased and retired, shares			(596,000)
Stock repurchased and retired, value		(7,436)	(7,436)
Issuances of common stock under stock plans and related tax benefit, shares			321,068
Issuances of common stock under stock plans and related tax benefit, value		882	882
Cash dividends on common stock		(38,324)		(38,324)
BALANCE, VALUE at Dec. 31, 2012		1,724,039	1,512,400	187,293	24,346
BALANCE, SHARES at Dec. 31, 2012			111,889,959
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		98,361		98,361
Other comprehensive income (loss), net of tax		(29,322)			(29,322)
Stock-based compensation		5,017	5,017
Stock repurchased and retired, shares			(584,677)
Stock repurchased and retired, value		(9,360)	(9,360)
Issuances of common stock under stock plans and related tax benefit, shares			667,921
Issuances of common stock under stock plans and related tax benefit, value		6,428	6,428
Cash dividends on common stock		(67,737)		(67,737)
BALANCE, VALUE at Dec. 31, 2013		1,727,426	1,514,485	217,917	(4,976)
BALANCE, SHARES at Dec. 31, 2013		111,973,203	111,973,203
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		147,520		147,520
Other comprehensive income (loss), net of tax		17,044			17,044
Stock issued in connection with merger, shares	[1]		104,385,087
Stock issued in connection with merger, value	[1]	1,989,030	1,989,030
Stock-based compensation		15,292	15,292
Stock repurchased and retired, shares			(403,828)
Stock repurchased and retired, value		(7,183)	(7,183)
Issuances of common stock under stock plans and related tax benefit, shares	[2]		4,206,658
Issuances of common stock under stock plans and related tax benefit, value	[2]	7,692	7,692
Cash dividends on common stock		(115,824)		(115,824)
BALANCE, VALUE at Dec. 31, 2014		$ 3,780,997	$ 3,519,316	$ 249,613	$ 12,068
BALANCE, SHARES at Dec. 31, 2014		220,161,120	220,161,120

[1] The amount of common stock issued in connection with the merger is net of $784,000 of issuance costs.

[2] The shares issued include 2,889,996 warrants exercised.