Investment Securities Maturity Schedule (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
Available-for-Sale, Amortized Cost
Due within one year		$ 129,520
Due after one year through five years		394,977
Due after five years through ten years		191,676
Due after ten years		559,843
Total before residential mortgage-backed securities		1,276,016
Total		2,238,067	$ 2,588,013
Available-for-Sale, Fair Value
Due within one year		129,979
Due after one year through five years		399,137
Due after five years through ten years		201,943
Due after ten years		583,373
Total before residential mortgage-backed securities		1,314,432
Total		2,292,079	2,610,760
Held-to-Maturity, Amortized Cost
Due within one year		0
Due after one year through five years		0
Due after five years through ten years		43,656
Due after ten years		636,051
Total before residential mortgage-backed securities		679,707
Amortized Cost		679,707	702,072
Held-to-Maturity, Fair Value
Due within one year		0
Due after one year through five years		0
Due after five years through ten years		45,926
Due after ten years		668,969
Total before residential mortgage-backed securities		714,895
Total		714,895	729,513
Residential mortgage-backed securities
Available-for-Sale, Amortized Cost
Residential mortgage-backed securities	[1]	962,051
Total		962,051	1,203,548
Available-for-Sale, Fair Value
Residential mortgage-backed securities	[1]	977,647
Total		977,647	$ 1,200,960
Held-to-Maturity, Amortized Cost
Residential mortgage-backed securities	[1]	0
Held-to-Maturity, Fair Value
Residential mortgage-backed securities	[1]	$ 0

[1] Residential mortgage-backed securities, which have prepayment provisions, are not assigned to maturity categories due to fluctuations in their prepayment speeds.