Parent Company Only Financial Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
ASSETS:
Cash and cash equivalents	$ 538,688				$ 299,878				$ 538,688	$ 299,878	$ 470,599	$ 411,583
Total assets	10,319,249				9,236,910				10,319,249	9,236,910	9,193,237
Liabilities and Shareholders' Equity [Abstract]
Junior subordinated debentures	245,299				245,294				245,299	245,294
Due to affiliates	4,284				4,229				4,284	4,229
Total liabilities and shareholders' equity	10,319,249				9,236,910				10,319,249	9,236,910
Income Statement [Abstract]
Interest expense	13,425	13,896	13,603	13,863	18,147	20,683	22,080	23,612	54,787	84,522	109,097
Net interest income	84,378	82,548	80,414	76,894	76,107	75,308	78,910	74,353	324,234	304,678	295,195
Noninterest expense	84,371	85,334	81,678	81,929	89,589	89,408	87,607	88,649	333,312	355,253	352,390
Income before income taxes	29,134	29,104	40,739	32,531	17,745	30,598	32,044	13,291	131,508	93,678	39,133
Income tax expense (benefit)	(6,980)	(8,056)	(12,978)	(9,853)	3,201	0	288,842	0	(37,867)	292,043	0
Net income	22,154	21,048	27,761	22,678	20,946	30,598	320,886	13,291
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities									412,789	(126,499)	84,072
Net cash (used in) provided by investing activities									(738,148)	1,054,928	378,401
Proceeds from stock issuance, net									868	661	0
Dividends paid									(59,195)	(49,743)	0
Net Cash Provided by (Used in) Financing Activities									564,169	(1,099,150)	(403,457)
Cash and Cash Equivalents, Period Increase (Decrease)									238,810	(170,721)	59,016
Parent Company [Member]
ASSETS:
Cash and cash equivalents	29,881				24,443				29,881	24,443	44,602	47,520
Investments in subsidiaries	1,416,724				1,417,025				1,416,724	1,417,025
Other assets	15,463				20,755				15,463	20,755
Total assets	1,470,339				1,470,530				1,470,339	1,470,530
Liabilities and Shareholders' Equity [Abstract]
Accrued expenses payable	7,454				3,072				7,454	3,072
Junior subordinated debentures					245,294					245,294
Due to affiliates	1,639				4,241				1,639	4,241
Shareholders' equity	1,215,947				1,217,923				1,215,947	1,217,923
Total liabilities and shareholders' equity	1,470,339				1,470,530				1,470,339	1,470,530
Income Statement [Abstract]
Interest income									216	268	300
Interest expense									6,034	6,785	6,433
Net interest income									(5,818)	(6,517)	(6,133)
Equity in net earnings of subsidiary									104,497	380,294	50,961
Noninterest expense									11,090	5,385	5,699
Income before income taxes									87,589	368,392	39,129
Income tax expense (benefit)									6,052	17,329	4
Net income									93,641	385,721	39,133
Statement of Cash Flows [Abstract]
Adjustments to reconcile net income to net cash used in operating activities									(102,676)	(412,528)	(42,051)
Net cash provided by (used in) operating activities									(9,035)	(26,807)	(2,918)
Payments to Acquire Interest in Subsidiaries and Affiliates									0	0	0
Dividends from subsidiaries									72,800	52,600	0
Net cash (used in) provided by investing activities									72,800	52,600	0
Proceeds from stock issuance, net										3,791	0
Dividends paid										(49,743)	0
Net Cash Provided by (Used in) Financing Activities									(58,327)	(45,952)	0
Cash and Cash Equivalents, Period Increase (Decrease)									5,438	(20,159)	(2,918)
Parent Company [Member] | Other Investments [Member]
ASSETS:
Investments in subsidiaries	$ 8,271				$ 8,307				$ 8,271	$ 8,307