Significant Accounting Policies and Recently Issued Accounting Pronouncement - (Details) - USD ($)	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jan. 02, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Recently Issued Accounting Pronouncements
Mortgage servicing rights, at fair value	$ 2,926,790,000	$ 2,556,253,000	$ 2,720,335,000	$ 2,905,090,000	$ 2,820,612,000	$ 2,785,964,000	$ 2,486,157,000	$ 2,354,489,000
Income taxes payable	504,569,000	480,559,000	441,336,000	414,636,000	400,546,000	74,158,000	67,357,000	58,956,000
Stockholders' equity	$ 2,061,507,000	$ 1,911,613,000	$ 1,778,997,000	$ 1,701,192,000	$ 1,653,791,000	$ 1,916,710,000	$ 1,861,944,000	$ 1,794,199,000			$ 1,719,674,000	$ 1,399,356,000
Adjustment | Accounting Standards Codification 250 Mortgage Servicing Rights Fair Value
Recently Issued Accounting Pronouncements
Mortgage servicing rights, at fair value										$ 848,000
Income taxes payable									$ 72,000
Stockholders' equity									$ 776,000