Summarized Quarterly Results of Operations (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest Income
Mortgage-backed and credit risk transfer securities	$ 191,490	$ 194,938	$ 200,737	$ 185,492	$ 174,511	$ 160,416	$ 147,548	$ 149,003	$ 772,657	$ 631,478	$ 521,547
Commercial and other loans	1,291	1,353	1,484	1,582	1,593	1,672	4,051	4,222	5,710	11,538	23,508
Total interest income	192,781	196,291	202,221	187,074	176,104	162,088	151,599	153,225	778,367	643,016	545,055
Interest Expense
Repurchase agreements	97,993	112,851	117,978	101,875	91,057	81,763	69,389	59,585	430,697	301,794	163,881
Secured loans	8,808	10,413	11,258	11,144	10,565	9,490	8,471	6,927	41,623	35,453	19,370
Exchangeable senior notes	0	0	0	0	0	0	0	1,621	0	1,621	13,340
Total interest expense	106,801	123,264	129,236	113,019	101,622	91,253	77,860	68,133	472,320	338,868	196,591
Net interest income	85,980	73,027	72,985	74,055	74,482	70,835	73,739	85,092	306,047	304,148	348,464
Other income (loss)
Gain (loss) on investments, net	(148,511)	202,413	302,182	268,382	76,957	(207,910)	(36,377)	(160,370)	624,466	(327,700)	(19,704)
Equity in earnings of unconsolidated ventures	427	403	702	692	624	1,084	798	896	2,224	3,402	(1,327)
Gain (loss) on derivative instruments, net	188,682	(177,244)	(344,733)	(201,460)	(293,485)	87,672	67,169	133,367	(534,755)	(5,277)	18,155
Realized and unrealized credit derivative income (loss), net	2,896	1	(2,438)	7,884	(9,026)	4,975	735	3,165	8,343	(151)	51,648
Net loss on extinguishment of debt	0	0	0	0	0	0	0	(26)	0	(26)	(6,814)
Other investment income (loss), net	909	1,005	1,007	1,029	850	1,068	(2,160)	3,102	3,950	2,860	7,381
Total other income (loss)	44,403	26,578	(43,280)	76,527	(224,080)	(113,111)	30,165	(19,866)	104,228	(326,892)	49,339
Expenses
Management fee — related party	10,529	8,740	9,370	9,534	10,294	10,105	10,102	10,221	38,173	40,722	37,556
General and administrative	1,882	1,862	1,999	2,258	2,116	1,673	1,525	1,756	8,001	7,070	7,190
Total expenses	12,411	10,602	11,369	11,792	12,410	11,778	11,627	11,977	46,174	47,792	44,746
Net income (loss)	117,972	89,003	18,336	138,790	(162,008)	(54,054)	92,277	53,249	364,101	(70,536)	353,057
Net income (loss) attributable to non-controlling interest	0	0	0	0	(899)	(681)	1,163	671	0	254	4,450
Net income (loss) attributable to Invesco Mortgage Capital Inc.	117,972	89,003	18,336	138,790	(161,109)	(53,373)	91,114	52,578	364,101	(70,790)	348,607
Dividends to preferred stockholders	11,106	11,107	11,106	11,107	11,106	11,107	11,106	11,107	44,426	44,426	28,080
Net income (loss) attributable to common stockholders	$ 106,866	$ 77,896	$ 7,230	$ 127,683	$ (172,215)	$ (64,480)	$ 80,008	$ 41,471	$ 319,675	$ (115,216)	$ 320,527
Net income (loss) attributable to common stockholders
Basic (in usd per share)	$ 0.75	$ 0.57	$ 0.06	$ 1.05	$ (1.54)	$ (0.58)	$ 0.72	$ 0.37	$ 2.42	$ (1.03)	$ 2.87
Diluted (in usd per share)	$ 0.75	$ 0.57	$ 0.06	$ 1.05	$ (1.54)	$ (0.58)	$ 0.72	$ 0.37	$ 2.42	$ (1.03)	$ 2.75