Annual report pursuant to Section 13 and 15(d)

Repurchase Agreements Repurchase Agreements Outstanding Balances and Key Metrics (Details)

v2.4.1.9
Repurchase Agreements Repurchase Agreements Outstanding Balances and Key Metrics (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 12,932,463us-gaap_AssetsSoldUnderAgreementsToRepurchaseRepurchaseLiability $ 12,250,450us-gaap_AssetsSoldUnderAgreementsToRepurchaseRepurchaseLiability
Assets Sold under Agreements to Repurchase, Weighted Average Borrowing Rate, Excluding U.S. Treasuries and Interest Rate Swaps 0.72%two_AssetsSoldUnderAgreementsToRepurchaseWeightedAverageBorrowingRateExcludingUSTreasuriesAndInterestRateSwaps 0.75%two_AssetsSoldUnderAgreementsToRepurchaseWeightedAverageBorrowingRateExcludingUSTreasuriesAndInterestRateSwaps
Assets Sold under Agreements to Repurchase, Weighted Average Remaining Maturity, Excluding U.S. Treasuries and Interest Rate Swaps 64two_AssetsSoldUnderAgreementsToRepurchaseWeightedAverageRemainingMaturityExcludingUSTreasuriesAndInterestRateSwaps 72two_AssetsSoldUnderAgreementsToRepurchaseWeightedAverageRemainingMaturityExcludingUSTreasuriesAndInterestRateSwaps
Assets Sold under Agreements to Repurchase, Interest Rate 0.64%us-gaap_AssetsSoldUnderAgreementsToRepurchaseInterestRate 0.69%us-gaap_AssetsSoldUnderAgreementsToRepurchaseInterestRate
US Treasury Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 1,996,250us-gaap_AssetsSoldUnderAgreementsToRepurchaseRepurchaseLiability
/ us-gaap_AssetsSoldUnderAgreementsToRepurchaseAxis
= us-gaap_USTreasurySecuritiesMember
$ 997,500us-gaap_AssetsSoldUnderAgreementsToRepurchaseRepurchaseLiability
/ us-gaap_AssetsSoldUnderAgreementsToRepurchaseAxis
= us-gaap_USTreasurySecuritiesMember
Assets Sold under Agreements to Repurchase, Interest Rate 0.23%us-gaap_AssetsSoldUnderAgreementsToRepurchaseInterestRate
/ us-gaap_AssetsSoldUnderAgreementsToRepurchaseAxis
= us-gaap_USTreasurySecuritiesMember
0.03%us-gaap_AssetsSoldUnderAgreementsToRepurchaseInterestRate
/ us-gaap_AssetsSoldUnderAgreementsToRepurchaseAxis
= us-gaap_USTreasurySecuritiesMember