Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Securities available for sale	$ 2,484,773	$ 2,323,371
Equity securities
Securities available for sale	21,514	47,623
U.S. Government securities
Securities available for sale	0	200
U.S. Government sponsored agency securities
Securities available for sale	25,136	214
State and municipal securities
Securities available for sale	262,765	245,215
Corporate debt securities
Securities available for sale	96,955	98,034
Collateralized mortgage obligations
Securities available for sale	821,509	902,313
Mortgage-backed securities
Securities available for sale	1,158,835	928,831
Auction rate securities
Securities available for sale	98,059	100,941
Fair Value, Measurements, Recurring
Mortgage loans held for sale	16,886	17,522
Securities available for sale	2,484,773	2,323,371
Other financial assets	50,594	38,987
Total assets	2,552,253	2,379,880
Other financial liabilities	48,924	38,821
Fair Value, Measurements, Recurring | Equity securities
Securities available for sale	21,514	47,623
Fair Value, Measurements, Recurring | U.S. Government securities
Securities available for sale		200
Fair Value, Measurements, Recurring | U.S. Government sponsored agency securities
Securities available for sale	25,136	214
Fair Value, Measurements, Recurring | State and municipal securities
Securities available for sale	262,765	245,215
Fair Value, Measurements, Recurring | Corporate debt securities
Securities available for sale	96,955	98,034
Fair Value, Measurements, Recurring | Collateralized mortgage obligations
Securities available for sale	821,509	902,313
Fair Value, Measurements, Recurring | Mortgage-backed securities
Securities available for sale	1,158,835	928,831
Fair Value, Measurements, Recurring | Auction rate securities
Securities available for sale	98,059	100,941
Fair Value, Measurements, Recurring | Level 1
Mortgage loans held for sale	0	0
Securities available for sale	21,514	47,623
Other financial assets	16,129	17,682
Total assets	37,643	65,305
Other financial liabilities	15,914	17,737
Fair Value, Measurements, Recurring | Level 1 | Equity securities
Securities available for sale	21,514	47,623
Fair Value, Measurements, Recurring | Level 1 | U.S. Government securities
Securities available for sale		0
Fair Value, Measurements, Recurring | Level 1 | U.S. Government sponsored agency securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 1 | State and municipal securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Collateralized mortgage obligations
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Mortgage-backed securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 1 | Auction rate securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 2
Mortgage loans held for sale	16,886	17,522
Securities available for sale	2,361,864	2,166,899
Other financial assets	34,465	21,305
Total assets	2,413,215	2,205,726
Other financial liabilities	33,010	21,084
Fair Value, Measurements, Recurring | Level 2 | Equity securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Government securities
Securities available for sale		200
Fair Value, Measurements, Recurring | Level 2 | U.S. Government sponsored agency securities
Securities available for sale	25,136	214
Fair Value, Measurements, Recurring | Level 2 | State and municipal securities
Securities available for sale	262,765	245,215
Fair Value, Measurements, Recurring | Level 2 | Corporate debt securities
Securities available for sale	93,619	90,126
Fair Value, Measurements, Recurring | Level 2 | Collateralized mortgage obligations
Securities available for sale	821,509	902,313
Fair Value, Measurements, Recurring | Level 2 | Mortgage-backed securities
Securities available for sale	1,158,835	928,831
Fair Value, Measurements, Recurring | Level 2 | Auction rate securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3
Mortgage loans held for sale	0	0
Securities available for sale	101,395	108,849
Other financial assets	0	0
Total assets	101,395	108,849
Other financial liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Equity securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Government securities
Securities available for sale		0
Fair Value, Measurements, Recurring | Level 3 | U.S. Government sponsored agency securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3 | State and municipal securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt securities
Securities available for sale	3,336	7,908
Fair Value, Measurements, Recurring | Level 3 | Collateralized mortgage obligations
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3 | Mortgage-backed securities
Securities available for sale	0	0
Fair Value, Measurements, Recurring | Level 3 | Auction rate securities
Securities available for sale	$ 98,059	$ 100,941