Securities Available-for-Sale (Tables)

12 Months Ended

Dec. 31, 2012

Securities Available-for-Sale and Investment Securities Held-to-Maturity [Abstract]

Summary of Securities Available-for-Sale

	December 31, 2012								December 31, 2011
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
	(dollars in thousands)
U.S. Treasury	$	2,000	$	4	$	—	$	2,004	$	1,999	$	13	$	—	$	2,012
U.S. Government Sponsored Enterprises		130,048		360		68		130,340		174,657		311		11		174,957
SBA Backed Securities		8,043		113		—		8,156		8,714		87		—		8,801
U.S. Government Agency and Sponsored Enterprises Mortgage-Backed Securities		1,212,953		20,816		412		1,233,357		1,020,752		16,262		1,176		1,035,838
Privately Issued Residential Mortgage-Backed Securities		2,938		31		22		2,947		3,509		—		311		3,198
Obligations Issued by States and Political Subdivisions		55,855		41		722		55,174		21,515		84		957		20,642
Other Debt Securities		2,300		—		47		2,253		13,293		—		683		12,610
Equity Securities		458		112		—		570		533		85		—		618
Total	$	1,414,595	$	21,477	$	1,271	$	1,434,801	$	1,244,972	$	16,842	$	3,138	$	1,258,676

Maturity distribution of securities available-for-sale

The following table shows the estimated maturity distribution of the Company’s securities available-for-sale at December 31, 2012.

	Amortized		Fair
	Cost		Value
	(dollars in thousands)
Within one year	$	69,122	$	69,314
After one but within five years		1,073,778		1,091,554
After five but within ten years		258,646		261,371
More than ten years		11,092		10,539
Nonmaturing		1,957		2,023
Total	$	1,414,595	$	1,434,801

Continuous unrealized loss position for 12 months or less and 12 months or longer

	December 31, 2012
	Less Than 12 Months				12 Months or Longer				Total
			Unrealized				Unrealized				Unrealized
Temporarily Impaired Investments	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
	(dollars in thousands)
U.S. Government Sponsored Enterprise	$	34,967	$	68	$	—	$	—	$	34,967	$	68
U.S. Government Agency and Sponsored Enterprise Mortgage-Backed Securities		93,006		383		10,169		29		103,175		412
Privately Issued Residential Mortgage-Backed Securities		—		—		1,863		22		1,863		22
Obligations Issued by States and Political Subdivisions		—		—		3,963		722		3,963		722
Other Debt Securities		—		—		1,453		47		1,453		47
Total temporarily impaired securities	$	127,973	$	451	$	17,448	$	820	$	145,421	$	1,271

	December 31, 2011
	Less Than 12 Months				12 Months or Longer				Total
			Unrealized				Unrealized				Unrealized
Temporarily Impaired Investments	Fair Value		Losses		Fair Value		Losses		Fair Value		Losses
	(dollars in thousands)
U.S. Government Sponsored Enterprise	$	14,989	$	11	$	—	$	—	$	14,989	$	11
U.S. Government Agency and Sponsored
Enterprise Mortgage-Backed Securities		331,469		1,176		—		—		331,469		1,176
Privately Issued Residential Mortgage-Backed Securities		—		—		3,198		311		3,198		311
Obligations Issued by States and Political Subdivisions		—		—		3,725		957		3,725		957
Other Debt Securities		10,542		652		1,468		31		12,010		683
Total temporarily impaired securities	$	357,000	$	1,839	$	8,391	$	1,299	$	365,391	$	3,138