Summary of Quantitative Inputs and Assumptions for Items Categorized in Level III of Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 7,186,737	$ 12,649,547
Fair Value, Measurements, Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	10,995,682	16,940,420
Fair Value, Measurements, Recurring | Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	1,243,635	1,388,672
Fair Value, Measurements, Recurring | Level 3 | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	163,135	239,659
Fair Value, Measurements, Recurring | Level 3 | Other Investments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 66,973	$ 65,821
Default Rate	2.00%	2.00%
Pre-paymentRate	20.00%	20.00%
Recovery Lag	12 months	12 months
Recovery Rate	70.00%	70.00%
Reinvestment Rate	4.00%
Fair Value, Measurements, Recurring | Level 3 | Other Investments | Transaction Price Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 30,430	$ 29,572
Fair Value, Measurements, Recurring | Level 3 | Minimum | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	8.40%	7.10%
Fair Value, Measurements, Recurring | Level 3 | Minimum | Other Investments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	0.00%	0.70%
Reinvestment Rate		4.00%
Fair Value, Measurements, Recurring | Level 3 | Maximum | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	10.10%	10.30%
Fair Value, Measurements, Recurring | Level 3 | Maximum | Other Investments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	15.00%	13.00%
Reinvestment Rate		4.13%
Fair Value, Measurements, Recurring | Level 3 | Weighted Average | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	9.10%	8.80%
Fair Value, Measurements, Recurring | Level 3 | Weighted Average | Other Investments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	2.00%	2.20%
Reinvestment Rate		4.01%
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 963,151	$ 1,029,371
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Assets Of Consolidated CLO Vehicles | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 38
Discount Rate	9.00%
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Assets Of Consolidated CLO Vehicles | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets		$ 8,277
EBITDA Multiple		7
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Assets Of Consolidated CLO Vehicles | Third Party Pricing Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 410,843	$ 499,624
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Equity Securities | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	100,064	91,753
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Equity Securities | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 851	$ 862
EBITDA Multiple	8.0	8
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Equity Securities | Other
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 23,468	$ 17,536
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Equity Securities | Transaction Price Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	15,889	21,716
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Partnership And LLC Interests | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 298,692	$ 293,744
Exit Multiple - NOI	12.5	12.5
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Partnership And LLC Interests | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 530	$ 530
Book Value Multiple	1.0	1.0
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Partnership And LLC Interests | Other
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 20,122	$ 22,346
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Partnership And LLC Interests | Transaction Price Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	7,928	14,070
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Partnership And LLC Interests | Third Party Pricing Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	677	758
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Debt Instruments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 19,567	$ 6,122
Revenue CAGR	6.60%	7.70%
Exit Capitalization Rate		8.30%
Exit Multiple - NOI	12.0	12.0
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Debt Instruments | Transaction Price Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 2,090	$ 1,897
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Debt Instruments | Third Party Pricing Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 62,392	$ 50,136
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Minimum | Equity Securities | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	7.10%	7.10%
Revenue CAGR	(1.20%)	1.00%
Book Value Multiple	0.010
Exit Capitalization Rate	5.00%	5.00%
Exit Multiple - EBITDA	2.8	4.0
Exit Multiple - NOI	8.8	8.8
Exit Multiple - P/E	10.0	9.5
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Minimum | Equity Securities | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Book Value Multiple	0.8	0.8
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Minimum | Partnership And LLC Interests | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	4.60%	4.60%
Revenue CAGR	(2.10%)	(22.20%)
Book Value Multiple	0.085
Exit Capitalization Rate	1.50%	3.10%
Exit Multiple - EBITDA	0.1	0.1
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Minimum | Debt Instruments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	8.20%	6.60%
Exit Capitalization Rate	4.20%
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Maximum | Equity Securities | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	32.10%	31.40%
Revenue CAGR	41.00%	49.40%
Book Value Multiple	0.095
Exit Capitalization Rate	11.40%	11.40%
Exit Multiple - EBITDA	16.0	16.0
Exit Multiple - NOI	12.5	12.5
Exit Multiple - P/E	17.0	17.0
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Maximum | Equity Securities | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Book Value Multiple	0.9	0.9
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Maximum | Partnership And LLC Interests | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	26.50%	26.50%
Revenue CAGR	54.40%	71.50%
Book Value Multiple	0.093
Exit Capitalization Rate	25.00%	10.00%
Exit Multiple - EBITDA	16.6	15.0
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Maximum | Debt Instruments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	20.00%	18.40%
Exit Capitalization Rate	8.30%
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Weighted Average | Equity Securities | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	12.80%	12.60%
Revenue CAGR	7.30%	7.10%
Book Value Multiple	0.079
Exit Capitalization Rate	8.20%	8.50%
Exit Multiple - EBITDA	10.0	9.9
Exit Multiple - NOI	10.5	10.5
Exit Multiple - P/E	14.3	11.0
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Weighted Average | Equity Securities | Market Comparable Companies
Fair Value, Option, Quantitative Disclosures [Line Items]
Book Value Multiple	0.9	0.9
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Weighted Average | Partnership And LLC Interests | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	9.80%	9.80%
Revenue CAGR	7.60%	8.40%
Book Value Multiple	0.091
Exit Capitalization Rate	5.70%	5.70%
Exit Multiple - EBITDA	9.6	8.6
Fair Value, Measurements, Recurring | Level 3 | Consolidated Blackstone Funds | Weighted Average | Debt Instruments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	9.90%	9.60%
Exit Capitalization Rate	6.60%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 11,092	$ 8,886
Default Rate	2.00%	2.00%
Pre-paymentRate	20.00%	20.00%
Recovery Lag	12 months	12 months
Reinvestment Rate	400.00%	400.00%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Third Party Pricing Valuation Technique
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value assets	$ 8,854	$ 15,363
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Minimum | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate		5.10%
Recovery Rate	30.00%	30.00%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Minimum | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	0.30%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Maximum | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate		6.30%
Recovery Rate	70.00%	70.00%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Maximum | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	5.90%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Weighted Average | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate		5.40%
Recovery Rate	67.30%	68.10%
Fair Value, Measurements, Recurring | Level 3 | Corporate Treasury Investments | Weighted Average | Loans and Receivables | Discounted Cash Flows
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount Rate	4.80%