Derivative Instruments (Details 2) (Derivative instruments not accounted as hedges under GAAP, USD $) In Thousands, unless otherwise specified	6 Months Ended	8 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	$ 4,123,203	$ 4,181,800
Interest rate swaps
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	2,301,050	2,811,800
Average Fixed Pay Rate (as a percent)	1.40%	1.20%
Average Maturity (years)	7 years 1 month 6 days	7 years 2 months 12 days
Forward Starting (as a percent)	23.90%	25.00%
Interest rate swaps | Greater than 1 year and less than 3 years
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	556,100	762,800
Average Fixed Pay Rate (as a percent)	0.40%	0.40%
Average Maturity (years)	1 year 8 months 12 days	2 years 3 months 18 days
Forward Starting (as a percent)	26.80%	22.70%
Interest rate swaps | Greater than 1 year and less than 3 years | Minimum
Average fixed pay rate and average maturity for the Company's interest rate swaps
Remaining Interest Rate interest rate swap Term	1 year	1 year
Interest rate swaps | Greater than 1 year and less than 3 years | Maximum
Average fixed pay rate and average maturity for the Company's interest rate swaps
Remaining Interest Rate interest rate swap Term	3 years	3 years
Interest rate swaps | Greater than 3 years and less than 5 years
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	411,400	439,500
Average Fixed Pay Rate (as a percent)	0.90%	0.80%
Average Maturity (years)	4 years 7 months 6 days	4 years 9 months 18 days
Forward Starting (as a percent)		10.20%
Interest rate swaps | Greater than 3 years and less than 5 years | Minimum
Average fixed pay rate and average maturity for the Company's interest rate swaps
Remaining Interest Rate interest rate swap Term	3 years	3 years
Interest rate swaps | Greater than 3 years and less than 5 years | Maximum
Average fixed pay rate and average maturity for the Company's interest rate swaps
Remaining Interest Rate interest rate swap Term	5 years	5 years
Interest rate swaps | Greater than 5 years
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	1,333,550	1,609,500
Average Fixed Pay Rate (as a percent)	1.90%	1.70%
Average Maturity (years)	10 years 2 months 12 days	10 years 2 months 12 days
Forward Starting (as a percent)	30.10%	30.10%
Interest rate swaps | Greater than 5 years | Minimum
Average fixed pay rate and average maturity for the Company's interest rate swaps
Remaining Interest Rate interest rate swap Term	5 years	5 years
Interest rate swaption
Average fixed pay rate and average maturity for the Company's interest rate swaps
Number of derivative instruments	4
Interest rate swaption one
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	75,000
Average Maturity (years)	1 month
Fixed pay swap agreement term	10 years
Interest rate swaption two
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	222,500
Average Maturity (years)	3 months
Fixed pay swap agreement term	20 years
Interest rate swaption three
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	750,000
Average Maturity (years)	5 months
Fixed pay swap agreement term	10 years
Interest rate swaption four
Average fixed pay rate and average maturity for the Company's interest rate swaps
Notional Amount	$ 166,500
Average Maturity (years)	35 months
Fixed pay swap agreement term	7 years