Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 208,690	$ 120,823
Other comprehensive income, net of tax:
Net unrealized (losses) gains arising during period from debt securities available for sale	(41,859)	26,933
Less: reclassification adjustment for net gains on sale of debt securities available for sale in net income	0	0
Net change in net unrealized holding (losses) gains on debt securities available for sale	(41,859)	26,933
Change in unamortized net holding losses on debt securities held to maturity	2,019	666
Unamortized unrealized net holding losses on debt securities available for sale transferred to debt securities held to maturity	30,487	0
Less: non-credit related impairment on debt securities held to maturity	200	0
Change in unamortized non-credit related impairment on debt securities held to maturity	130	223
Net change in unamortized holding losses on debt securities held to maturity	(28,538)	889
Unrealized holding losses arising during period from cash flow hedge instruments	(237)	(9,866)
Change in defined benefit plans	(3,379)	(485)
Other comprehensive (loss) income, net of tax	(74,013)	17,471
Comprehensive income	134,677	138,294
Less: comprehensive income attributable to noncontrolling interests	461	443
Comprehensive income attributable to BBVA Compass Bancshares, Inc.	$ 134,216	$ 137,851