Fair Value (Details 7) (MSRs, Initial recognition, Level 3, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair value
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Unpaid principal balance of underlying loans	$ 315,869	$ 4,217	$ 318,066	$ 17,504
Weighted-average servicing fee rate (as a percent)	0.31%	0.27%	0.31%	0.28%
Fair value | Minimum
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	7.40%	7.50%	7.40%	7.50%
Annual total prepayment speed (as a percent)	8.80%	8.40%	8.80%	7.80%
Life	3 years 7 months 6 days	6 years 4 months 24 days	3 years 7 months 6 days	5 years 10 months 24 days
Annual per-loan cost of servicing	68	68	68	68
Fair value | Maximum
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	13.10%	9.90%	13.10%	9.90%
Annual total prepayment speed (as a percent)	17.20%	9.50%	17.20%	9.50%
Life	7 years	6 years 8 months 12 days	7 years	6 years 10 months 24 days
Annual per-loan cost of servicing	120	100	120	100
Fair value | Weighted average
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	9.90%	7.80%	9.90%	8.40%
Annual total prepayment speed (as a percent)	9.20%	9.20%	9.20%	8.60%
Life	6 years 10 months 24 days	6 years 4 months 24 days	6 years 10 months 24 days	6 years 4 months 24 days
Annual per-loan cost of servicing	101	71	101	77
Amortized cost
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Unpaid principal balance of underlying loans	4,120,962	2,485,982	12,350,104	4,811,328
Weighted-average servicing fee rate (as a percent)	0.30%	0.27%	0.29%	0.27%
Amortized cost | Minimum
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	5.40%	7.50%	5.40%	7.50%
Annual total prepayment speed (as a percent)	8.50%	8.40%	8.50%	7.80%
Life	2 years 10 months 24 days	6 years 4 months 24 days	2 years 10 months 24 days	5 years 10 months 24 days
Annual per-loan cost of servicing	68	68	68	68
Amortized cost | Maximum
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	15.90%	9.90%	15.90%	9.90%
Annual total prepayment speed (as a percent)	14.70%	9.50%	18.50%	9.50%
Life	6 years 10 months 24 days	6 years 8 months 12 days	6 years 10 months 24 days	6 years 10 months 24 days
Annual per-loan cost of servicing	120	100	120	100
Amortized cost | Weighted average
Key assumptions used in determining the fair value of MSRs at time of initial recognition
Pricing spread (as a percent)	8.20%	9.80%	8.20%	9.80%
Annual total prepayment speed (as a percent)	8.80%	8.40%	8.80%	8.30%
Life	6 years 8 months 12 days	6 years 8 months 12 days	6 years 8 months 12 days	6 years 8 months 12 days
Annual per-loan cost of servicing	$ 104	$ 99	$ 102	$ 99