Investment Securities (Details 2) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Held-to-maturity debt securities amortized cost disclosures
Due after one year through five years, held-to-maturity debt securities amortized cost	$ 2,400,000		$ 2,400,000
Amortized cost, held-to-maturity debt securities	2,400,000		2,400,000		$ 2,400,000
Held-to-maturity debt securities, Estimated fair value disclosures
Due after one year through five years, held-to-maturity debt securities, Estimated fair value	2,400,000		2,400,000
Estimated Fair Value	2,400,000		2,400,000		2,400,000
Available-for-sale debt securities amortized cost disclosures
Due after five years through ten years, available-for-sale debt securities amortized cost	757,000		757,000
Due after ten years, available-for-sale debt securities amortized cost	292,522,000		292,522,000
Residential mortgage-backed securities, amortized cost	4,170,907,000		4,170,907,000
Equity securities, amortized cost	28,075,000		28,075,000
Amortized cost, Available for sale securities	4,492,261,000		4,492,261,000		4,894,428,000
Available for sale debt securities, Estimated Fair Value Disclosures
Due after five years through ten years, available-for-sale debt securities, Estimated Fair Value	836,000		836,000
Due after ten years, available-for-sale debt securities, Estimated Fair Value	305,169,000		305,169,000
Residential mortgage-backed securities, Estimated Fair Value	4,197,674,000		4,197,674,000
Equity securities, Estimated Fair Value	29,104,000		29,104,000
Estimated fair value, Available for sale securities	4,532,783,000		4,532,783,000		$ 4,911,963,000
Amortized cost of available for sale investment securities pledged	1,858,273,000		1,858,273,000
Fair value of available for sale investment securities pledged	1,874,111,000		1,874,111,000
Proceeds from sales and calls of available for sale securities	0	$ 253,292,000	30,282,000	$ 621,588,000
Proceeds from sales of mortgage-backed securities	0	253,292,000	23,992,000	620,933,000
Gross gains realized on sales	0	0		9,479,000
Gross losses realized on sales	$ 0	$ 6,446,000	$ 428,000	$ 8,196,000