Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized CostAvailable-for-sale Securities, Gross Unrealized GainsAvailable-for-sale Securities, Gross Unrealized LossesAvailable-for-sale Securities, Debt Securities
2007Debt and Securites Other than Mortgage-backed Securities [Member]US Government Agencies Debt Securities [Member]3,295,00030,00003,325,000
US States and Political Subdivisions [Member]47,620,000331,00041,00047,910,000
US Government-sponsored Enterprises Debt Securities [Member]294,223,0001,289,00048,000295,464,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]1,678,828,00012,414,0006,771,0001,684,471,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]312,973,00008,533,000304,440,000
Mortgage-backed Securities [Member]1,991,801,00012,414,00015,304,0001,988,911,000
Other Debt Securities [Member]228,421,000172,0001,013,000227,580,000
Major Types of Debt and Equity Securities [Domain]2,565,360,00014,236,00016,406,0002,563,190,000
2006Debt and Securites Other than Mortgage-backed Securities [Member]US Government Agencies Debt Securities [Member]19,036,0007,000103,00018,940,000
US States and Political Subdivisions [Member]38,833,000125,000178,00038,780,000
US Government-sponsored Enterprises Debt Securities [Member]258,938,000125,0001,167,000257,896,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]1,626,206,0002,982,00030,808,0001,598,380,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]364,687,00007,923,000356,764,000
Mortgage-backed Securities [Member]1,990,893,0002,982,00038,731,0001,955,144,000
Other Debt Securities [Member]333,131,000101,0006,115,000327,117,000
Major Types of Debt and Equity Securities [Domain]2,640,831,0003,340,00046,294,0002,597,877,000
2005Debt and Securites Other than Mortgage-backed Securities [Member]US Government Agencies Debt Securities [Member]4,455,00017,00037,0004,435,000
US States and Political Subdivisions [Member]33,240,00054,000334,00032,960,000
US Government-sponsored Enterprises Debt Securities [Member]96,103,000142,000569,00095,676,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]1,686,626,0004,366,00030,028,0001,660,964,000
Mortgage-backed Securities, Issued by Private Enterprises [Member]427,019,00008,131,000418,888,000
Mortgage-backed Securities [Member]2,113,645,0004,366,00038,159,0002,079,852,000
Other Debt Securities [Member]333,418,000127,0008,253,000325,292,000
Major Types of Debt and Equity Securities [Domain]2,580,861,0004,706,00047,352,0002,538,215,000