Securities (Fair value and gross unrealized losses) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Available-for-sale Securities
Less than 12 months, fair value	$ 101,946	$ 461,003
Less than 12 months, unrealized (losses)	(882)	(21,912)
12 months or more, fair value	281,226	37,423
12 months or more, unrealized (losses)	(14,734)	(4,637)
Total, fair value	383,172	498,426
Total, unrealized (losses)	(15,616)	(26,549)
Held-to-maturity Securities
Less than 12 months, fair value	30,732	211,326
Less than 12 months, unrealized (losses)	(657)	(18,293)
12 months or more, fair value	158,417	22,579
12 months or more, unrealized (losses)	(10,108)	(2,421)
Total, fair value	189,149	233,905
Total, unrealized (losses)	(10,765)	(20,714)
U.S. Government agency securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	0	110,435
Less than 12 months, unrealized (losses)	0	(13,661)
12 months or more, fair value	140,743	22,579
12 months or more, unrealized (losses)	(8,362)	(2,421)
Total, fair value	140,743	133,014
Total, unrealized (losses)	(8,362)	(16,082)
Agency CMOs [Member]
Held-to-maturity Securities
Less than 12 months, fair value	29,115	98,082
Less than 12 months, unrealized (losses)	(646)	(4,465)
12 months or more, fair value	16,438	0
12 months or more, unrealized (losses)	(1,717)	0
Total, fair value	45,553	98,082
Total, unrealized (losses)	(2,363)	(4,465)
Municipal securities [Member]
Held-to-maturity Securities
Less than 12 months, fair value	1,617	2,809
Less than 12 months, unrealized (losses)	(11)	(167)
12 months or more, fair value	1,236	0
12 months or more, unrealized (losses)	(29)	0
Total, fair value	2,853	2,809
Total, unrealized (losses)	(40)	(167)
U.S. Government agency securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	0	8,077
Less than 12 months, unrealized (losses)	0	(918)
12 months or more, fair value	31,642	21,849
12 months or more, unrealized (losses)	(2,353)	(3,151)
Total, fair value	31,642	29,926
Total, unrealized (losses)	(2,353)	(4,069)
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	8,363	62,500
Less than 12 months, unrealized (losses)	(2)	(3,295)
12 months or more, fair value	32,423	0
12 months or more, unrealized (losses)	(896)	0
Total, fair value	40,786	62,500
Total, unrealized (losses)	(898)	(3,295)
Agency CMOs [Member]
Available-for-sale Securities
Less than 12 months, fair value	86,500	363,993
Less than 12 months, unrealized (losses)	(859)	(16,182)
12 months or more, fair value	205,715	15,574
12 months or more, unrealized (losses)	(11,033)	(1,486)
Total, fair value	292,215	379,567
Total, unrealized (losses)	(11,892)	(17,668)
Municipal securities [Member]
Available-for-sale Securities
Less than 12 months, fair value	7,083	26,433
Less than 12 months, unrealized (losses)	(21)	(1,517)
12 months or more, fair value	11,446	0
12 months or more, unrealized (losses)	(452)	0
Total, fair value	18,529	26,433
Total, unrealized (losses)	$ (473)	$ (1,517)