Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Allowance for uncollectible accounts	$ 1,778	$ 11,178
Accumulated depreciation, non-utility property	120	2,307
Accumulated depreciation, nuclear fuel	36,411	26,247
Accumulated depreciation, other intangible assets	0	5,414
Cumulative preferred stock of subsidiary, stated value	$ 100	$ 100
Cumulative preferred stock of subsidiary, shares authorized	10,000,000	10,000,000
Cumulative preferred stock of subsidiary, shares issued	115,293	115,293
Cumulative preferred stock of subsidiary, shares outstanding	115,293	115,293
Convertible preferred stock, stated value	$ 0	$ 0
Convertible preferred stock, shares authorized	10,000,000	10,000,000
Convertible preferred stock, shares issued	0	477,800
Convertible preferred stock, shares outstanding	0	477,800
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	79,653,624	86,673,174
Common stock, shares outstanding	79,653,624	86,673,174
Public Service Company of New Mexico [Member]
Allowance for uncollectible accounts	1,778	1,483
Accumulated depreciation, nuclear fuel	$ 36,411	$ 26,247
Cumulative preferred stock of subsidiary, stated value	$ 100	$ 100
Cumulative preferred stock of subsidiary, shares authorized	10,000,000	10,000,000
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	39,117,799	39,117,799
Common stock, shares outstanding	39,117,799	39,117,799
Cumulative preferred stock of subsidiary, shares issued	115,293	115,293
Cumulative preferred stock of subsidiary, shares outstanding	115,293	115,293
Texas-New Mexico Power Company [Member]
Cumulative preferred stock of subsidiary, shares authorized	1,000,000
Common stock, shares authorized	12,000,000	12,000,000
Common stock, shares issued	6,358	6,358
Common stock, shares outstanding	6,358	6,358
Common stock, par value	$ 10	$ 10